REQ's mysteriously being Deleted

Can anyone think of a reason why random PO Requisitions are randomly getting nuked?  I am the only one with a DELETE button so it's not like anyone is able to manual delete them.  We created an alert to find them when they are deleted but we just can't figure out WHY.

Luckily the products seem to have been ordered already, so that's good.  Just no idea what is causing them to vacate the premises.