Are you staying downtown downtown? Give me an idea of location and I can probably come up with some good post-concert spots within walking distance of the hotel.
My favorite vegan/veggie is Everest, a Nepalese place owned by a public health PhD. Delicious stuff, and very healthy. The location I know best is in the Grove neighborhood (along with plenty of cool bars, like the Atomic Cowboy right across the street), but they have a new location downtown on Olive for the office lunch crowd.
The strip of Washington Ave. where the 'nightlife' (or what passes in StL) resides is very close to the City Museum. I wouldn't call it an exactly typical St. Louis experience, but it can be a good time. (None of it is terribly cheap, but you won't get absolutely raked over the coals.) Places I dig on Washington for food/drinks: The Dubliner (Irish pub, decent food), Mosaic (solid food, tapas style, fancier), Wasabi (sushi, one of the best in town), Lucas Park Grille (if you can stand a bit of a see-and-be-seen crowd, or go early), Hair Of The Dog (dive bar - my people!)...
In the same basic area (you can walk from Wash Ave), at 10th and Olive is one of my favorite dive bars in town, Jack Patrick's. Home to one of the most diverse crowds in a St. Louis bar, decent pours, and a solid (internet) jukebox. Across 10th St. from JP's is a restaurant I've heard good things about, but haven't been to since I have a long-standing beef with the owner, Bailey's Range. (It's also, coincidentally, directly below the first apartment I got when I moved back to town after school.) The same owner also has a place a block North on Olive called The Bridge, with a focus on craft beers (I've heard sub-par food).
If you're mobile, get yourself to O'Connell's for a burger and a Guinness (and a Power's 12 year, neat, for me). Seriously, do it. Colleen can have a salad or something. It's a real-deal pub - the bar side was a former A-B public house that was moved from about 4 miles north; the whole building. No TV, slightly surly but charming waitresses, jazz on the speakers under the din of conversation from the ancient wooden booths, mounted animals and vintage bar paraphernalia. Nothing over-the-top, no kitsch in sight, just beautifully lived in. I've been going there since before I was born. Hell, that place may have a role in my conception for all I know. But really, if there's one place in town I'd miss if I moved away, it's O'Connell's.
If you're looking to venture any farther out of downtown, let me know and I'll be happy to help out.
As far as places to find Red Guitar Bread: nowhere at the moment, unfortunately. I put my baking operations on hiatus back in October to look for my own space. I have a building under contract, though, so it looks like I'm back in business by mid-April.