You know, I'd never thought about doing something like that. Tbh, that seems more helpful than most things; because you know where the person you're talking to is, and that you can go and see them in person. Like, you really shouldn't do that do a store clerk, that's not what they're being paid for; but at the same time, if I was in that position then I'd absolutely put my job on the line and take the time to talk and comfort them.
I wonder if LGBT-positive stores give people crisis training in case they get calls or emails like that. If not, then it might be worth considering doing that as a community. Then someone who's struggling can find their nearest LGBT-anything and have someone to talk to.
There's a queer anarchist bookstore in Asheville NC that's amazing for community. I'm not sure if they routinely field calls like that, but I know they're a space for community members to gather, to comfort one another, and to be a space when space is what's needed. Called Firestorm. They're really amazing .