The passing of a celebrity reminds me of the odd secular alternative to "my prayers are with [newly dead person's] family." "Prayers" makes sense...if you believe, then you want people to pray for you, especially in trying times. But "thoughts"?
I guess it's nice to know people are worried about you. But it still sounds jarring to my ears. Not that saying "prayers" to/as a non-believer would be at all preferable, but I think I'd stick with a simple "I'm sorry."