iserith
Magic Wordsmith
So they never miss a secret door?
Sure - when they don't search for one or don't search in the right place. (There is no roll in either case.) In my group's current adventure, they have missed at least one so far and I even telegraphed it. They were more interested in other things in the scene and moved on.
In general, if they're at least searching in the area and have committed an appropriate amount of time and effort to the task, I will say their attempt has an uncertain outcome, ask for a roll, and narrate progress combined with a setback if they fail the check.
If they fail the check and I tell them there are no secret doors, then we're back to what lowkey13 is saying: That the call for a check is saying at a "metagame" level that there is a secret door. At which point, some DMs might consider kludges like saying "No metagaming!" or "No retries!" or start making those rolls for the players. I don't need to employ any of those if I just adjudicate as I described above.