Q: "Do you have any juice?"  
A: "Yes, **there's** some in the fridge."

Sounds perfectly fine to me, but:

Q: "Do you have any towels?"  
A: "Yes, **there's** some in the closet."

Does not.

I asked for towels - plural - so wouldn't "Yes, **there're** some in the closet," in which **there are** is turned into a contraction be the correct way to say it?

Spellcheck, however, doesn't like "there're", and I think I'm the only person I've ever heard use the word "there're".  Even folks who I know say "there are" shorten it to "there's" when possible.

Am I saying it wrong, or are both forms acceptable?