svn add foo.txt
svn add bar.txt
rm foo.txt
# wait 3 weeks
svn commit -m 'add bar.txt to my repo'

svn: Commit failed (details follow):
svn: File '/home/chris/repo/foo.txt' is missing

Now you know that the instruction to add foo.txt into the repo is hidden in one or more .svn directories and it will be a massive PITA to locate and manually edit these files to remove the broken add so here is the solution...
svn revert foo.txt

Reverted 'foo.txt'

Adding   bar.txt
Sending  bar.txt
Transmitting file data ........
Committed revision 1.

# And Relax!