Try searching for the app by its actual name - RadioID (one word), not radio id.
Actually, its Radio (space) Id, 2 words, as seen in google play and Itunes..
Also, it will come up if you search iPhone only.
If you still have trouble or don't want to spend the dollar, there are the following PC programs to try out..
2 Tone Detect A Windows program that detects two-tone pages, records audio, and sends the recording to email or cell phones.
2 Tone Finder A companion program for TwoToneDetect that assists in finding unknown tone sets.
FiveTone Detect A Windows program that detects five tone pages, records audio, and sends the recording to email or cell phones.