Yep. In the fix I linked I set it up to default to a word if it fails the template instead, so it'll then check for a match to that word ("fail") and if so it just falls back to 5 minutes and will tell me as much.
Going to be a hell of a lot better about that in the future though. Was definitely a rookie mistake on my part to assume that just because it'd worked every time I'd tested it, used it, and with timers and all thus far that it would always work 100% of the time. Why assume when you can validate? I do in code I write... Guess I don't think about it in the same way with HA as much, oops.