Automatic Teller Machine is a misnomer. It's automatic, and it's a machine, but it's no teller. A teller would have looked at my check and made sure that it had been endorsed before accepting it. Either the people who designed the machines (I think the main producer of these devices is Diebold, whose owners I suspect of taking delight in the thought that their products create so much bother) didn't think its functions through, or they simply didn't have the technology (or decided it would be too costly) to equip the machine to scan a check for an endorsement and to spit it back out if it lacked one.
Teller is an interesting word. The verb to tell historically meant either to inform, to tell (recount) a story, or to tell (count) numbers. The verb to tally is also related. Likewise, a tale could be either a story or an accounting of numbers. So a bank teller can both tell your money and tell you "Hey, asshole, you didn't endorse this check!" (the bank teller would, of course, say it more politely; that's just the way I phrased it to myself while looking in the mirror after I had realized what I'd probably done.)
I suppose there'll be a fee associated with this, and a delay of indeterminate length, and I'd better get some cash into the account before I write any checks this month. What a pain in the arse the early stages of Alzheimer's can be!