If it is a deadbolt that must be unlocked by key from the INSIDE of the house, it might be a safety issue if there are no other escape routes from that room. If that is the case, then call for a repair or replacement of that deadbolt.
Tell them to leave the spare key in the lock, viola, just as good as a thumb bolt. The old rule of thumb from a builders standpoint is that a double keyed deadbolt is used in a door with glass in it or beside it (sidelights) etc. We always made it a point to encourage the homeowners to keep the key within reach, and make a point of using the key when the familiy did fire escape practice.
Recently ran into this. The subject was a row home with a double keyed cylinder lock on the front door. Called the FHA hotline and they referred me to the local office for this area. They told me that if the local building code requires a single cylinder deadbolt on the FRONT door, then FHA requires it. The local [FONT='Arial','sans-serif']ordinance[/FONT] called for a single cylinder so I called for the lock to be changed.