I suppose you are already onto this, but there might be more to this whole episode?
I am wondering (as you might be) if the detector is actually ok, and there is a real problem in the LP system or stove somehow. Say there is a real propane leak and that is why the alarm kept going off.
Could more propane be coming out than is being burned with the burner on low? Something. When you reset the alarm would that open the propane valve again? Did you smell the propane this time because you were just outside at a lower height than when inside where you might not smell it being higher? These may be wrong notions--I am no expert on propane issues for sure--but IMO just replacing the alarm now might not be the fix.
