Interesting phone number... and easy enough to see how long of a call and at what time it was placed if you were interested.
I know you're smart enough to make sure it wasn't one of your kids calling her kids (if that's applicable).
The hardest and best thing to know is that it's none of your business. In your own home you can have boundaries which are appropriate. I'm still a little amazed that I told my spouse he's not allowed in the house. He usually comes in and stays by the doorway.
What boundaries do you need to set to feel safe in your home. To have the home environment that works for you and your children?
Him relaxing and wanting to take care of you is in your best interest in a mediation/divorce process. That might sound cold, but when he's motivated, you profit.
What he's doing is none of your business. It's your time to heal, to get unstuck and move forward. Where he lands is his choice.
