I had this happen for a few weeks & decided rather than get, um, pissy about it...I would go with the flow...sorry, punsville tonight...and bought several different types of the Poise brand liners. The ones with "wings" worked the best; and since there are several different kinds for different troubles (they are clearly marked on their packaging), it was easy to find out what I needed.
Don't panic about it & don't stress...it's just another day in the life of living with MS.