I think there is a fairly simple process, perhaps it was embee who described it, whereby you can program a new key to your ECU, which I assume means that some ID data from the ECU is lodged into the HISS chip in the key. However, I am not sure if there is a unique ID for each key which goes the other way and is remembered by the ECU and can therefore later be wiped. If not, as you say the bike will be vulnerable. Hopefully this is not the case, and there is a unique ID for each key that a dealer can wipe from the ECU. This link would suggest that keys do have codes which are held in the EC