I used to frequent a coffee shop. I would get iced tea, sit at one of the sidewalk tables, smoke cigs, and pick an acoustic guitar to pass the time. There was an employee in the coffee shop, and one day she asked me to play guitar in the new band she was forming. It was just her on guitar/vox and a drummer at the time. She wanted a second guitarist, or maybe to just be a standalone singer while someone else played guitar; I'm not sure exactly.
I was kind of non-commital about it. I wasn't necessarily trying to be in a band, and I had this crazy girlfriend at the time who was pretty much a big distraction and energy suck, so it was hard to devote myself to much else seriously.
I did go to a few of their early gigs as a two-piece. I learned the songs that way, and at the coffee shop, I casually played examples of her songs to show that I had picked them up. She, being less of a formally trained musician than I was, was kind of blown away that someone could learn her songs just by watching a gig, with no instrument in hand. At that point, if I had shown the slightest bit of additional initiative or proactivity, I think the gig would have been mine, easily. But I didn't bother acting too interested...and she never hounded me about it (not something she would do, given her personality). As she played more and more gigs as a two piece, I believe she started to think that the band would be fine that way.
I swear it was not two months later, but the band was picked up and was all over the local big "alternative" radio station here in L.A. Everyone who listened to K-ROQ knew them. (FWIW, I was not a K-ROQ listener; I listened to oldies radio.) They didn't stay in the mainstream too long, but they retained popularity on independent stations after their initial 15 minutes of semi-mainstream fame. I think they toured, put out an album or two, made a music video or two. They remained a two piece until they disbanded.
I still drop her a line on Facebook every few years just to say hey. From what I understand, she's gone through a whole lot of major crap since those coffee shop days. It's quite sad to me, having known her and really liked her before all that band stuff. But, I'm glad she's still alive and making music. She was a really sweet person in her own bitter, sarcastic way (something I greatly appreciate).
I'm not sure I actually wish I had joined...but that was pretty close to stumbling into being a "pro" at a relatively young age. Who knows where it would have led.