Hi, I don't understand the question: in the asm code for the transponder you have both the packet read by the decoder and the transponder number. Keep in mind that this 'easy' decoding is valid only for RC3 transponders.
For RC4 such relation does not exist, since the packet sent is always different (but repeating in the long run). I'm working on this fact to record RC4 passages.

By the way, nice work you're doing with ESP32. Only thing that you might want to beware is that size of send buffer seems to be 64 records (bits), so you need to extend it by setting RMT_MEM_SIZE_CHn > 1.