Short answer: the intersection of language evolution with petty concerns such as "making sense".
Historically, Germanic languages had only two tenses, past and non-past. All the complicated German tenses were invented relatively recently (centuries ago), and have begun to be discarded again, at least in colloquial speech.
It's for much this reason that the tenses called "perfect" and "imperfect" are treated exactly the same in speech, with preference between the two dictated by prosody and structure concerns rather than by actual meaning, whereas in English they actually do mean different things.
Another consequence is that the "future tense" they teach in school is vanishingly rare in spoken German. The literary way of saying this would be "Ich werde anrufen...", but the future is usually only implied. This occurs in English too, but it's not nearly as common. Think of "The concert ends at 9", where the present is used to imply a future because actual present wouldn't make any sense. This German sentence works much the same way.
The reason that this construct definitely implies future, rather than a simple present, is "falls". Translating "falls" as "if" does a bit of disservice to the word; it's much more specific than that - "I call you if I find it" can be interpreted as meaning that every time I find this object, I call you. "Falls" cannot perform this function. The most accurate English translation of "falls" that I can think of is as an English phrase: "in the event that". And "I call you in the event that I find it" just screams that it's missing a future, don't you think?
Basically, yes. In your sentence, the call happens before the finding. The call is made to prepare for the possibility that the thing is found. In "Ich rufe an, falls ich es finde", the call happens after the finding. It's what will be done in the event that the thing is found. So it definitely translates to "I'll call if I find it."
I think "in case" focuses on countermeasures already made, whereas "falls" focuses on contingency plans. (Probably the best way to translate "in case" is "für den Fall".)
I very much like and agree with your comments. But would a more simple explanation be that in German the 'Present Simple' tense is used to express a promise or reassurance (which implies future action) whereas in English we'd use "I'll .."? For instance "Ich mache es" v "I'll do it".
It seems to me that the action of calling depends on the finding, so logically I WILL call (in the future) if I find it. As of now, I have not found it yet. So if one day I happen to find wathever it is we're talking about, I WILL call. It makes sense to me and it reminds me of this: http://www.englishkitab.com/en/Essential_Grammar/Double_Future.html
The translation, "I am calling, if (in the event) you find it" would satisfy the present tense "requirement" for the verb call, without having to use the future tense of "I will call". Obviously, the process of calling would happen in the future, because it is predicated on something that might happen in the future ("if/in the event I find it").
I guess this one of those in grammar rules might be analogous to "the spirit of the law vs the letter of the law".
I have zero linguistic background, but I think this really speaks to what you have shared with us about the evolution (past and ongoing) of the German language, and also the fact that German and English verbs can not be lined up tense by tense and equivalently translated (because the two languages do not both have the same set of tenses for verbs.)
I know I am splitting hairs. Your explanation was excellent and I really appreciate those contributors such as yourself that do such a great job to help us learn German!
I know your post is from 6 years ago, and that you probably have moved on from this. And when I post a reply to a very old post, I feel like I am opening a door to an old abandoned house and yelling, "Hello, is anyone there?"
well it is not wrong per se but there is a problem:
rufen can mean " to shout"
but we have a verb + preposition
and in german you will find the whole verb in infinitive as "anrufen"
but the preposition will get splitt off if it is used as predicate
and anrufen means "to call (somebody [via telephone])"
"Falls" is in general a much more restrictive "wenn". It can be used only with the present indicative, and maybe the future, though I'd just use the present as an implied future there, as in "falls du morgen Zeit hast". Not sure about that, but definitely not past or conjunctive. (Notice that "falls" comes from the genitive of "Fall", which means "case". So it's kind of like "in the case that".) Provided that it's grammatically usable, "falls" feels less likely than "wenn". It's also got a bit of an "if and only if" feel sometimes.
"Wenn du studierest, bestehst du die Prüfung."
If you replace "Wenn" with "Falls", it sounds like you might doubt that the person is going to study, and also implies a bit more than before that you can't pass the test without studying. But if the sentence had used "...studiert hättest...", "falls" would sound pretty nonsensical.
Thanks :) I was actually reading about this last night and I found this page which was also helpful:
Another helpful explanation: https://yourdailygerman.wordpress.com/2012/11/20/falls-meaning/