Yes I get this from time to time. I find that because I haven't recently had any structure or my usual routine that when I get back to sorting myself out simple things can really make me sleep for ages and hours. I some how slept 14 hours after just walking to the beach and reading a book as a set goal, I think that's the longest I've slept. Other times I can be so tired for no reason however at those times I know if I don't push myself out of bed then I really am going to be stuck in a rut again. I think that once in a while this is fine and nothing to worry about but when it happens more than once too often then it becomes a problem. I don't think you have anything to feel guilty for sometimes our bodies need catching up time and they don't work to a clock. So I think your body probably needed some extra sleep on just this occasion. Sorry if this wasn't helpful to you.