Frankie had been her mother's dog

Already to familiar, so she might as well sign it and seal it up. She could already see the surprise in Margot’s honeyed eyes.

Too familiar. This story is great! Good luck!

Hi Hannah,

So I'm finally here to review your contest entry story. Sorry it took me so long!

I liked the feeling of sadness your story arose in me. I'm not sure whether it was meant to be this way, but nonetheless.. I like sad stories and this one makes you feel a tiny hole somewhere in your soul. I really pitied Katarin who couldn't get in touch with her mom..

I have some small comments about the structure of some of your sentences though.

He usually sat underneath the bench at the side of the room and woke up to snap at waiting customers who forgot he was there, when they slid their feet back under the bench and caught him in his stomach.

I think you don't need a comma before when. When-clauses (I'm not too good at explaining, sorry for that) are usually marked by a comma if they precede the main clause, but in your case it's the opposite. Anyway, this sentence is rather longish and over-informative. Try splitting it up into two. I'm not a fan of long sentences myself, I actually think it's an art to be able to write a cohesive and beautiful long sentence

But she hadn’t heard from her mother since the storm, had no idea where she would be, embarrassed to ask after a homeless drunk she was unfortunately and blessedly related to.

Firstly, this sentence just came out of the blue. You start it with a but and tell us about her mother suddenly... Maybe try to come up to this point logically then? Or just get rid of the but and start the sentence with "Katarin hadn't heard..."
Secondly, what comes after this clause... I didn't really understand what you meant. Maybe it's just silly me who was crelated to a drunk? Katarin? Her mom? What does it have to do with all that..? Very confusing...

She dialed the number of the pay phone where her mother was supposed to be, the number her mother had written on an old chip bag.

Again, not really clear why her mother was supposed to be waiting for the call at some random pay phone if she went missing after the storm?

***

Now, my point is that the story is very interesting and intriguing, but lacks coherence in some places and it's difficult to understand what's really going on. So I suggest splitting up longer sentences and adding some more details at places I mentioned above.

Most probably you had the same problem as I did with my contest story... the 1,000 words limit. It's really hard to put a great idea into such constraints

Keep writing! Wish you best of luck in the contest! Hope we both win