I live in NY and yorkies are dognapped all the time. One story was in Central park..... a man walked up to the dog on the leash....bent down to pet it...... whipped out a pair of scissors and cut the lead and in one quick swoop.... grabbed the yorkie and ran. Never found the guy. It was on the news years ago. I was in Central Park onec and a lady kept following me. I would turn to look at her and she would pretend to look elsewhere..... but she kept following me..... I didn't let my baby down .... I was holding her the whole time and I think she was waiting for me to put her down. ALL my dogs are microchipped but I am still very careful about people.
Not to make you nervous but he could have lied to your mom about where he is or his intentions. Be careful.