The problem is that you do not indicate at what frequency your system works. To detect a carrier, an antenna is important. Sensitive detectors are abundant but your keychain should be able to get > -40 dBm from the antenna to achieve a reliable signal detection.
There are many RF sources around, from FM, UHF TV, door openers, radars, cell phones... You should also use a good filter to detect "your" signal among many interferers.
Logarithmic detectors like LTC5505 can detect RF signals from >-60 dBm, but many interference sources will trigger it rather than "your" signal.