Reporting ELT activation?

So, this past weekend, I was pre-flighting my aircraft and as I switched on the master to lower the flaps, my radios briefly fired up and I heard an ELT beacon on 121.5. I left the master on and double checked it on my GNS430 to confirm. Sure enough, it was an ELT. First thing I did was checked the four aircraft to which I had access in order to ensure they weren't activated by a hard landing. I noted two other aircraft out of their hangars at the time as well.

Due to the surrounding topography, I was unable to contact the nearest ATC while on the ground. The phone number I had for the tower was inactive as well. My next move was to contact the nearest FSS, but after 20 minutes on hold, I finally gave up. By the time I took off, the ELT was no longer transmitting. When I got into range, I let the tower at the local Class C know about the incident. The whole scenario got me thinking, if I were to run into the situation again, what is the correct procedure for reporting an active ELT?