This is a really interesting thread. I can definitely feel for your friend. I am one of those bassists who has been playing almost thirty years but don't know all the notes on the fretboard! But I can get around by feel.
I actually stopped playing from '96-2002 - about five years. When I started up again, I realized that although I have always listened to technical, virtuoso music - from Deep Purple, Rush & Yes to Stanley Clarke, Jaco Pastorius, Mahavishnu Orchestra, etc. - I also love the blues and straight-ahead rock 'n' roll, and part of what makes that music work is the attitude as opposed to the technique. When I got back into music, I realized that I had something to say on the instrument, and that I didn't have to just ride the coattails of the guitarist. Part of my growth was the other people I was playing with - in fact, that is such a huge part. I feel like after 25-30 years I am finally learning how to solo, but there are also times when I like to just groove and play a repetitive bass line over and over if that's what the music needs.
Another kind of music I have discovered is soul jazz - late-'60s/early-'70s stuff like the organ trio stuff by Jimmy McGriff, Brother Jack McDuff, later Grant Green, also like the music that came out on the CTI label. Finding a guitar player who is into this stuff and playing in a trio with him has forced me to practice, learn some new stuff, and solo a lot more! 10 years since I've re-started playing, I continue to find my voice, I feel so blessed to have a band to play with again, and continue to deepen my enjoyment of music.
I was fortunate to see Victor Wooten play but also went to his clinic - I felt like I understood a lot of what he talked about - it's about the music and being yourself, not about trying to sound like someone else. It's also about listening, learning and enjoying. I heard other people who were at the same clinic saying things like "after seeing him play I wanted to throw away my bass" and I felt like they didn't get it yet. I felt inspired to go home and practice for my band so that I could continue to improve my own playing, totally separate from anything technical that Victor did.
Sorry for the long-winded response, not sure if this is relevant to what your buddy is going through but it's what I thought about when I read this thread...