With any numbers station, and particularly with the Cubans, one (or even a couple) transmission does not make it a new frequency of use. Many numbers stations operators have errors in settings, accidental uses of frequencies and modes, and the Cubans seem to do this more than others. He is called Pedro for a reason.
The Cubans apparently use the same transmitters for Radio Habanna Cuba, their numbers transmissions, and some of their jammers. It is not all that uncommon for them to forget to change the freq, and for numbers to come up on a scheduled R. Habanna or jammer freq, or the other way around. Or other times their numbers (or R. Habanna, or a jammer) may appear one time on an oddball, unexplained, frequency and never be seen there again.
These days HM01 is pretty much AM only, but in the past the Cubans made many errors in transmission mode. M08a, V02a, and SK01 were all normally sent in AM, with M08a using MCW, a modulated 1 kHz tone instead of keying the transmitter off and on. To receive this M08a the listener had a few options, either tune to the correct frequency in AM mode, the correct frequency in either USB or LSB mode, or plus or minus 1 kHz in CW mode, it all worked. But sometimes, on a regular schedule, M08a had no AM carrier present. It was not keying the carrier on and off, as one does with true CW, but rather it was still using the 1 kHz modulation, but the transmitter was typically in LSB mode. In these cases the listener could tune to the same frequency as the AM transmission, but in LSB mode, or they could tune 1 kHz low and in CW mode. This led to some M08a schedules having more than one frequency listed, often 1 kHz apart.
What does the above have to do with errors in mode? Sometimes after an M08a (no carrier) transmission they would forget to switch out of LSB mode. Resulting in V02a and SK01 transmissions in LSB instead of AM. Sometimes they would catch these errors mid transmission, and you would see the signal go from LSB to AM without pause.
The Chinese have the same bad habit with V26. V26 transmissions are almost always preceded by 2 other transmissions, a Chinese 4+4 digital modem in LSB, and then M97 in CW. Sometimes the transmitter is left in LSB when switching form the 4+4 to M97, so the M97 ends up being 1 kHz low. M97/V26 transmits on 3 frequencies at once normally, all in the same modes, but one time I caught each freq in a different mode, one LSB, one AM, and one USB.
The point of all that rambling is that errors happen. Watch 7320 kHz and see if HM01 returns, but don’t be surprised if it never does. There do appear to be some frequency changes happening for HM01, but that might be normal as winter sets in, or possibly just as time goes on. Most numbers stations do change freqs over time, sometimes to keep up with seasonal propagation changes and other times for reason only they know.
T!