How do I moniter a new fish if I never see it?

[new but handy]

I got a new mandarin on fri, now I only ever see it at night when it lays down for bed. I'm not joking. I haven't seen it during the day since I put it in the tank. I watched it eating pods half an hour after I put it in the tank, but I literaly have not seen it once since. I can't find it so I can't keep an eye on it.