In English this is a sentence fragment. There is not enough information to make a complete sentence - we start with some sort of conditional phrase, but do not declare what happens when the condition is met.
Is it considered complete in Swedish? If so, what exactly does it mean?
I agree that this is a fragment in English, and as a result I was at first unsure if my translation could be correct. Is such a fragment accepted in Swedish?
How can we determine that its YOUR passport? Why not, "If you lose THE passport?"
It's ambiguous, we have to guess from the context. In this case, it could mean either lose or drop, but the first seems more likely.
Barnet har tappat en tand is normally 'The child has lost a tooth', not 'dropped', though it could possibly mean that too in the right context.
Jag tappade glaset och det gick sönder 'I dropped the glass and it broke', – lost is unlikely to be the right translation.
If you want to say 'lose' unambiguously, there's a particle verb: tappar bort. (stress on bort).
"Förlora" means losing in the sense of for example losing a football match or a contest. It can also mean losing something in the sense of not having something anymore, like "tappa", but to me it feels more permanent, like you lost your job or you lost a family member to a fire. You can also only "tappa" an object, if you briefly lose a person you use "tappa bort" like Arnauti has already explained.