Okay, so I'm not talking multiverse because, let's face it, that's a cop-out.
And I'm not talking Back to the Future/Primer either because... well... physics isn't my strong point but you can't create matter, right? If the concepts of Primer worked, they could've just used the machine to duplicate bars of gold bullion, in the same way the machine duplicated people.
I travel two weeks into the future. So during that two weeks, I effectively disappear (think I just contradicted myself, but go with me, okay?). In the future, I drop my wallet in the lab.
I travel back in time, to just after the moment I left.
Is my wallet in the future? When that moment arrives, will my wallet reappear?
(Can someone lend me $50? I can pay you back in a fortnight)