files deleted with no record?

I just encountered a situation where a merge was made, with no
apparent changes in files (ie no log), but the result was that some
files were deleted.



person A adds some files
person B adds some files from the same point
person B commits and pushes.
person A commits -- now merge is required
a few more commits on top of person B's commit
person A merges - this removes the files that B added. There is no log
of the files being deleted

Clearly this is possible - was this a user error?



Thanks