My email filter rule has been deleted

This morning I am getting junk emails that I know I set rules for. Looked in my email filter rule - and it is deleted! I did not delete this rule. The last spam email that was sent to the Spam folder as a result of my filter rules was 5/2 7:43PM. The first email that should have been sent to the Spam folder is 5/3 10:29AM.

1) Has this every happened before (filter rule deletion)?

2) Is there a way to recover the filter rule (I had a lot of work in it)?