I'm not sure I've ever come across this before either. It's not something I would say (I'm a native British English speaker). Perhaps it's a short form for "over there by the door", but it doesn't sound natural to me. I sort of understood what it meant, but had to look on here to check.
Is it an American English usage, or possibly a dialectal one?
It does but i would presume that you would know which definition us meant by context. If some says that someone or something is simply "borte", then rhey would likely mean "gone". But if "borte" was accompanied with "ved" (or perhaps another term?), you'd know that it mean "over (by)".