FREAKING OUT

Be
My fiancé has a son he sees every Wednesday he dropped him back off (his son) around 8:30. And he texted me saying he is going to swing by his own mothers house to say hi since she has been sick. Well he said he would be quick and it has been almost two hours! And he won't text me back or answer his phone. And his mom only lives 15 min away. I am freaking out. This is not like him to not answer his phone at least a text. He is glued to his phone at all times. I have extremely bad anxiety too and he knows that so for him to ignore me is surprisingly strange. 
UPDATE:::: so he did go to his mothers house but then stopped by his buddy's house afterwards he said he didn't tell me because he thought I would be crazy and ask him not to stay out late since he is known for that and I do tend to ask him sometimes not to stay out that late all the time because it's annoying and immature in my opinion. And he said he knew he would be home around 11 which he was so he thought it wasn't a big deal that he stopped at his buddy's house. I am still upset but I believe him him.
Thank you for all your comments though they did help me as I sat here nervously wondering where he was.