From what I've read, he didn't "try out" the mattress he wound up buying and I've heard of no other mattress (at that store or at the one before it) that he did test drive.
The first store he entered on Monday morning, probably around 9:15 or 9:30 was Willey (Willey's?) Furniture Store, 23011 W. 300 West, Salt Lake City. He left because he was told he couldn't take it with him right away. Then he went to another place nearby (one article said it was "across the street") which was Bradley's Sleep Etc, 2255 S. 300 West, SLC. Neither store sold hardware, according to what I've read.
I'm thinking that he WAS going to move to North Carolina -- and kill her along the way to keep her from exposing him.
But something came up.