Here's a link that might help:http://www.radioreference.com/apps/db/?aid=2247
but they say their data may not be accurate, so your travels might only serve to confirm that.
I have a database from at least 10 years ago that also shows 127.7 located at SIE VOR (N3905.73 W07448.02). I assume you have lat/long for the VORs and have driven to those locations, and not to a nearby city with the same name. From Google Earth it looks like SIE VOR is closer to Cape May than to Sea Isle City.
Depending on the height of the transmitter and the sensitivity of your receiver, you may have to be within 2-3 miles of the RCAG to hear anything. You could get an idea of your receiver performance by seeing how far from ACY, McGuire, PHL, PNE, etc. you can receive control tower transmissions.
There may be more than one RCAG available for a given frequency, and it's possible they were using another site when you happened to be there. The SIE site also shows 133.12, so if you can hear that one it may give you some clues.