Might have been a headcanon post, or a line from a ficlet. Probably on tumblr, although there's a chance it was from a longer piece on Ao3. Bucky almost feels like he’s involved somewhere? Not actually sure about that point.
Basically it boiled down to Tony had stopped telling Steve that tech/equipment/things he made for him were indestructible or unbreakable, because Steve just accepted that at face value. Didn’t test the claim deliberately, just used them with the assumption that they wouldn’t break, up until they did.