If they should credit everyone that did something that's used as a backdrop for a few seconds in a movie, they'd have time for little else. The guy who did a mural the main character walks by also doesn't get a credit.
Actually - that depends. Artists have sued (and successfully settled in some cases) for their artwork appearing as the background of other productions.
Yeah artists seem to do it all the time. They also often get indignant at the merest suggestion that they might want to agree for someone to use their work for free.
The difference is, of course, that writing code is joy so no wonder people will gladly do it and give the results away, whereas creating art is unpleasant, tiresome work, so it's an insult to suggest anyone would do it for reasons other than money.
http://www.hollywoodreporter.com/thr-esq/Maya-hayuk-lawsuit-...
I'm not saying I think he should pursue it in this case, just that the scenario you laid out isn't unprecedented.