Literally, "That was lacking/missing to me"; in more colloquial English "I missed that" (in the sense of feeling lacking, as in "I miss you!"), or "I was lacking that" (didn't have it when I needed it).
"Mi bezonis monon por iri al Francujo. Sed tio mankis al mi." (I needed money to go to France. But that was lacking to me [I didn't have any of that].)
"Kiam mi vojagxis, mi memoris la karesojn de mia patrino. Tio mankis al mi." (When I was travelling, I remembered the caresses of my mother. That was missing to me [I missed that].)
i dont think it works like that, since it has the same structure as french, maybe it is something like the verb "gustar" in spanish , saying "tu me gustas" doesn't mean "you like me" but rather "i like you"
The Italian "mancare" works the same way. Since the Esperanto "manki" shares the same root, I'd imagine it works the same way. "Mi mankas al vi" means "You miss me" (lit: "I am missing to you")
Could this mean "That was lost to me", i.e. "That went over my head", or does it literally mean that you were missing an object?
It can mean a literal object, or something more abstract, but the basic idea is not having something, or feeling a lack of something. So "That went over my head" isn't really the idea; one would say things like "mankas al mi tempo" (I don't have time), "mankas al mi mono" (I don't have [enough] money), or "mankas al mi mia amiko" (I miss my friend). It's quite a versatile construction, and pretty cool once you get used to it :-).
Edit: the word order is flexible: "tio mankis al mi", "mankis al mi tio", "al mi tio mankis", and "al mi mankis tio" all mean the same thing; the difference is merely stylistic.
I'm still confused on the accusative form. Why is it not 'tion'? Thanks in advance :)