My very own dog park?

I brought Monty out to play this afternoon and all of a sudden this young pup comes running into the yard.  A few sniffs and they became friends and were running through the yard like crazy.  While rolling over in play, I noticed the new friend was a she.  It took lots of running, but I finally was able to grab her enough to read her tag, she belongs to neighbors down the street but had not intention of being held.  She ran off.  Monty, I'm proud to say stayed in the yard.  I hope he would do that if I wasn't with him. She kept running in and out of the yard, playing with Monty.   He whined when he couldn't follow her.  I threw the tennis ball, she wasn't interested.  Monty went after it, ran past me, and dropped it at her feet!.  Well, in spite of treats and now a lead in hand, I wasn't able to catch her again.  Monty had a blast!  I hope she found her way home safely.  I'm sure we'll see her again.  Monty was so happy to play with his new friend.