For safety reasons the propane alarm HAS NO EXTERNAL FUSING TO THE 12 VOLT DC POWER SYSTEM. You don't want an unknown external blown fuse to keep your anti-explosion propane detector alarm to not work. There is an internal fuse in the propane detector, and the loss of (or low) 12 volts DC power will cause the propane detector to sound for a while until its internal backup battery runs out. (You hear the beeping from the detector and low batteries at a lot of RV storage facilities - That's why it is a good idea to disconnect the battery system in long term storage) Right now I can't remember how the propane detector gets it's power (direct connection to the battery??), but I'm sure some more in the know Heartlander will chip in. According to the Airstream and Keystone RV forums the propane detector should be direct wired to the battery with no fusing.
IF the hot wire for the propane detector is hot wired to the battery with no fuse in between, AND you inadvertently TOUCHED this hot wire directly connected to the hot side of your battery TO GROUND, you have created a dead short across your battery with the detector supply wiring, and I would have expected a good sized spark, some smoke, and that supply wire being melted apart somewhere. Your battery unfused can put out something like 200 amps. This shouldn't have affected the other 12 volt DC and 120 volt AC circuits, but with a high current fault, who knows?? The modern converter/chargers are microprocessor based, but do have like 3 large current protective fuses on the 12 volt output on the external area of the converter case, near the 12 volt output wiring connectors. The easiest and surest way to take the converter/charger out of the 12 volt circuit is to pull those fuses, short of disconnecting the 12 volt wiring which you have to be very careful no to touch to ground, as the battery is still connected to the 12 volt circuit. The 12 volt main non self resetting 50 amp circuit breaker should protect that wiring, though.
The logical way to troubleshoot loss of power is to start measuring at the power source and then work your way "downstream" until the point of power loss is detected. I would start with the AC circuits as they are partially responsible for creating the DC power through the converter/charger with the battery as a DC backup. Measure at the park pedestal , then maybe at the inside AC breaker box mains wiring by removing the breaker box surround trim. The mains breakers are usually on the left end of the breaker box, with 2 large feed wires attached to them and the neutral wire attached to the common neutral buss, and the ground wire attached to the ground buss. Between the park power outlet is your power cord connectors, your input power connector to your rig (or maybe the cord reel), under the trailer to the front storage area where the transfer switch or power protection relay (both optional) might be then on to the AC circuit breaker box mentioned before.
Your 12 volt DC system has 2 power sources, the charger/converter and the battery as power sources with the non-self resetting 50 amp circuit breaker on the DC buss bar with other SIMILAR self resetting 12 volt high current circuit breakers, but all the rest SELF RESET when the overload current condition is removed. That special circuit breaker for the battery/charger connection has a tiny black reset button on the side of it to reset it after an overload condition is encountered. That breaker is also unique in that the direction of DC current flow through it goes both directions: towards the battery from the charger when the batter is charging, and from the battery towards the 12 volt buss bar and charger, and 12 volt small loads on the inside 12 volt fusepanel when the converter/charger is not working and the battery is supplying all 12 volt DC power.
See page 5 of this document for a generic Heartland 120 volt AC wiring diagram. Only 1 outlet is shown, but there are lots of others connected to different breakers in the breaker box.
https://manuals.heartlandowners.org/manuals/User Guides/Electrical V2.pdf
Here is a good 12 volt DC resource from our library. See page 4 for the 12 volt DC generic diagram :