Very common for fish to hide when in a new tank, and even more normal for plecos which are naturally elusive! They don't really bury themselves beneath substrate, they are excellent at finding good hiding spots though! I have two L181 plecos and know the favourite hiding spot for one of them, but the other I have no idea where she typically hides, only see her when she appears for meals! So I wouldn't be surprised at all for a pleco to hide away in a new home - it would be way more unusual for it not to hide, I promise!
Try dropping a pleco wafer or some veg into the tank just before the usual lights out, and sit where you're close enough to see, but not so close as to spook 'em, and watch for a while, see if he appears. But it's also not unusual for fish not to be hungry for a few days in a new environment, and plecos can go for quite a while without food, so don't be alarmed if he doesn't appear when you try this either. Don't leave uneaten food in there for too long, since it doesn't take long for it t begin releasing ammonia and can cause an ammonia spike, so remove it after a hour or two if untouched.
Photo of the tank? Can point out some likely hidey spots! They do need some real driftwood in their tank to aid their digestion, so make sure you have some/get some ASAP. As a last resort you could gently move decor and see if you can find him in the tank, make sure he's not stuck in any decor (some fake decor can pose a risk of trapping a fish) but this is unlikely and not ideal to stress a fish out like that by searching for them, and moving into a new home is already stressful. So if you do try this, make it only a last resort, and try to do it gently and calmly, and back off and leave him be once you spot him!
Was just kicking myself a little because I know that some plecs are more herbivorous and others need meatier diets, and some switch as they age even, so I told myself I should google what kinda diet this one has, but was in a hurry and comment was already long, so I was lazy 
