Sparano was asked this in the post-game interview and he said they were thinking about challenging but they weren't sure there was enough evidence to overturn it and didn't want to risk losing a timeout which may have become ultra important. I think they only had 1 left at the time.
yeah and I think Sparano made the right call. There needs to be conclusive evidence to overturn the call and on a play like that nothing is conclusive. It's a HIGH risk challenge that I never see coaches win when they try it.