Does the guy I hooked up with really want to hear from me again?

I hooked up with an acquaintance I hadn't seen for awhile three nights ago, we've flirted in the past but for certain reasons weren't able to do anything about it. When he was leaving he asked when he would see me again. He didn't have his PDA so he put his number in mine and said to call him. Was this just an obligatory gesture or should I really call him?