His remark to dispatch was that he was returning to his vehicle, and I don't think he was expecting to meet the suspicious person there. Not saying that's wehre they met, just saying that the call paints a picture where Zimmerman was resigned to having lost visual contact, and was going to await police so he could point out where he last saw the suspicious person.
GPS on just Zimmerman wouldn't tell you "for sure" if he continued to follow the guy he lost sight of - and even GPS on both of them would not establish what each of them was seeing.
People keep saying he called 911. He did not. He called the police department itself as he always did in these situations. They said (and I quote) “You don’t need to do that.”
The first thing cops would have asked him was “What did he look like?” The second & third would have been “What was he doing and where did he go?”
The “What was he doing?” part is murky at best. Most have TM just walking along. I don’t think a statement by Mr Z has been released saying just why he thought TM was acting suspicious. Do you have one?
In a majority minority neighborhood it would not be unusual to see a black youth with a hoody walking around - night or day. Just that would not cause Z to focus on TM.