Falling out of bed

Last night Ethan fell out of bed - not sure how it happened. Karri and I were in the living room talking about how good the transition to no bedrails had been, when we heard a thump and crying. I went up and he was climbing back in to bed. I gave him a quick cuddle and a kiss and tucked him back in. This morning Ethan claimed he slept well, but that his covers had slid off the bed - no recollection of falling. Guess he was OK.