You know, I was a young math prodigy, but it was always obvious to me even very young that a lot of people who had more on the ball than I did had a great deal of difficulty learning math, and soon it was obvious to me why - it's a very, very abstract thing!

I have a brilliant book on teaching math from the 1960s or 70s, where the writer compares a lot of mathematics teaching to teaching a deaf child how to play the piano by rapping their knuckles when they got it wrong. Probably a lot of kids would be smart enough to figure out how to fake it, but they would have no idea why anyone would ever want to do this activity, and hate it ever afterwards.

I think your idea of a processing disorder seems quite likely. I think it is the rare person who does not have some type of processing disorder. From reading writers like Oliver Sacks, one of the ways that people with deficits improve is by personally coming up with planned tricks and strategies that take their specific disorder into account.

I used to have a terrible problem just leaving things on buses and the like. It went on for years when I was a kid.

Eventually I developed this habit of constantly re-checking to see if I had the thing I was carrying, and always checking everywhere whenever there was a transition. I to psych myself up, "In two stops, I'm going to start to get up, and then I'm going to make sure I have everything, and then I will get out on the step after that," that sort of thing.

And eventually it worked, and years later I don't even worry about it, I do it automatically.

If numbers disappear, you should perhaps embrace this to figure out how it happens, and how to work around it. The very first time it happens next, maybe stop, and put on your detective hat? "What just happened? Did something trigger this? Could I develop some habit, some trick, some tick, that would automatically handle this?"