Toddler woke up screaming in night and was UNDER his crib?

This is super weird. My 2.5 year old sleeps really well and rarely wakes up in the night. Yesterday he skipped his nap (weird for him) and went to bed normal time. It’s now about 1:30am and I was woken up by him screaming at the top of his lungs. I figured he’d lost his blanket and was cold or something, but when I went in his room I saw just his feet sticking out from UNDER his convertible toddler bed. His whole body was under there in a space that’s only about 6-7” tall, so he was screaming because he couldn’t get himself out as there was no room to move. I slid him out and even had to lift the bed a little to get his head out. He clutched on to me and sobbed for a minute and now he’s calmed down but is still awake. I’m freaked out because I have no clue how he got under there into such a small space. Obviously he put himself there… but like, how?? Why?! Did he do it in his sleep?! It was so so weird. Anyone have this happen? Can toddlers crawl into tiny spaces like that? What.the.hell.