Update: Found safe and sound!
“Dear PoPville,
Matilda was staying with a friend in Capitol Hill while I am in California for a wedding. She got out Saturday morning and has been missing ever since. We live in Union Market. So, I am thinking she may somehow make her way to Union market district and might be seen wandering around loose.
She was last seen near Congressional Cemetery at 11am and 2pm Saturday.
She’s a black, medium sized cockapoo/terrier.”