It might be possible, but it depends on how the tech did the reinstall. Whenever you delete a file from an operating system, it doesn't actually erase that data. Instead the files are simply renamed so the PC will recognize that as free space to use. So there's a chance the data is still there, and there are a number of free unerase programs. However, once the file allocation table (sort of like a hard drive's 'table of contents') has specified that data as free "unallocated" space, it can be written to. And once the data is overwritten, it can't be recovered. If the tech did a reformat and reinstall, then chances are it's already been overwritten.
It doesn't take long before the data would become overwritten, so if you ever lose a file, don't do anything! Install an unerase program on a separate disk ASAP to try and recover the file. Remember, if you install the unerase software on your hard drive you run the risk of it overwriting the file you want to recover. It also might not take long before the operating system writes over that data, after just a couple of months it's probably already too late.
A good general rule is to make sure to backup the data on your computer before bringing it in for repair.