Happens to me occasionally over the last few weeks, some times more than others.
Latest batch i uploaded 141 and the website shows 94 actually there even 48hrs on from the upload.
Same issue using the fotolia or adobe FTP details.
The main pain is working out WHICH are missing to reupload.
EDIT:- It's just done it again. Uploaded 101 photos via FTP, 44 appear to keyword and submit, the others just vanished. No errors reported.