Unfortunately, none of the above suggestions seems to have remedied my loss of ignore list data. I have tried the /saveini , I have tried exiting mIRC manually (quitting) and not just restarting the machine without exiting the program. It seems after a reboot / restart, the ignore list is gone. This is important to me because there is a particularly toxic person in a channel I frequent that has a very negative impact on me. The majority of whatever this person types is not good and even seeing just a few lines of text before re-ignoring has an affect.
If any solution to this is known or is found, please let me know.