It'd probably be helpful to provide the seed that caused this in order for the matter to be better investigated. Cards not appearing seems to be an issue that happens rarely enough that Hempuli hasn't been able to replicate it. Giving the seed that causes the issue, however, would really aid in nailing down the problem. If it happens again, just exit the solitaire game you're in by pressing esc, go to settings, and copy the seed there before you try a new game/another game. Paste that seed here.
Oh, I've had a missing card issue as well, although I forgot to take a screenshot the two times it happened... I suspect it's an issue with autostack, as for me the missing card was always actually existing but just in the right pile, invisible. So I suspect the 3 of hearts is there in knutaf's screenshot, just invisible on top of the 2 of hearts. But yeah, two times in Tap Solitaire, I've pressed autostack and then thought one card was missing, but it was just not visually showing on the right pile. And it's always on the right pile that they're invisible... Maybe this is a different issue, but still, hope this helps! (also this is on Mac and 1.4d)