Campaign Schedule Deleted

I was just curious if anyone has had an issue with a batch schedule being removed from a campaign.  We had a campaign that was set to run daily and was working fine for a couple of months and then we noticed it had stopped running.  When we looked at the schedule, it was gone....like it had never been set up.  Our other campaigns were fine, it was just this one.  We only have two people that have admin access to this and neither one of us removed it.  Gremlins?  Anyone else have this problem before?