Perhaps he was worried that he didn’t hide the body well enough? I hope they are able to find out where he went and search the area!
He does not seem to be the type to have a girlfriend stashed away. From everything that has been reported so far - he was a controlling husband. He probably had a raging explosion sometime on Sunday afternoon - with just enough time to come up with the wild camping alibi and has been sticking with it.
As you suggested, he may have felt compelled to go back to wherever he left the body to make sure it is still hidden. Still controlling!!!!