Welcome to the AndroidForums, trojan081.
Hmm, there are utilities than can try to identify and recover deleted files (one called "Recuva" comes to mind), but you've usually got to have minimal activity on the storage device so that the freed-up blocks are not re-used by other files (thereby corrupting/confusing who "owns" the previously deleted blocks).
It probably also depends on how the files were erased or if the card was formatted and/or zeroed-out, etc. (i.e., a security wipe) that will determine if any files are recoverable.
As far as identifying whether or not the card is/was yours or not, you'd have to find a file or files on it that you know were unique and identifiable just to you.
Cheers!