Ermmm, not sure what the problem is.
Finding an AirTag in the greater scheme works by it pinging random iPhones, if yours was the only one in the house and out of range there is nothing that can be done. On top of that the pinging can't happen at short intervals cos otherwise battery life would suck.
The short range stuff only works for current iPhones and is indeed rather short range.
Bottom line, if you had really lost your keys the tag would have popped up at one point.
Finding an AirTag in the greater scheme works by it pinging random iPhones, if yours was the only one in the house and out of range there is nothing that can be done. On top of that the pinging can't happen at short intervals cos otherwise battery life would suck.
The short range stuff only works for current iPhones and is indeed rather short range.
Bottom line, if you had really lost your keys the tag would have popped up at one point.