Fallen en lost hamster!

[Fritselthehamster]

Okay, so I just got home and went straight to my hamster. Normally when I call him he comes. He just doesn't come and eventually I look into the house. He's not in it. I look further and eventually get everything out of the cage, so he is just not in it. The cage is on a cupboard and I think it is more than a meter high. The lid is also still on and seems normal. The lid has ventilation, but not something he would fit through. I can't find him and just start looking in my room, moving all the cupboards. I suddenly see him sitting on the ground when I turn and put him back in the cage. I don't understand how he escaped.

Wednesday morning at 9 am I left home and saw him. Thursday afternoon I come home at 5 o'clock and realize that he is lost. I had stayed overnight with a friend. Fortunately I found him within half an hour.
Now I am very concerned that he must have fallen over a meter (3 feet 3⅜ inches) high from the lid, he has not had any drinks and food in the meantime. The temperature has been reasonable.

He is not tame yet (he is 2 months old, my first hamster) and I cannot inspect him properly yet. In the cage he immediately started eating his favorites sweets that I put down (sunflower seeds, walnut and peanut). I haven't seen him drink yet. He is very active and ran a lot on his wheel (normaly he runs from 18.00-06.00 with breaks) as usual, also around the toys. However, he was randomly 'frozen' for a minute, during which he did not move. This was about 5 minutes after I put him in the cage. I don't want to bother him now. I also do not see that he uses a leg less. His eyes also seem to see clearly and normally. So if there is anything it seems internal to me. How can I be sure?

I removed the shelf and other tall objects and reinforced the lid and made it better closed (by putting something on it). All space in between is less than 1 cm. Also, in case he does come out, I put blankets on the floor to break the fall.

Should I be concerned? I have found many answers on how do I find my hamster? But not on what should I do when I find my hamster again?