I might or might not be an example of someone who has done that. I learned to play guitar from scratch at 28 years old. However, I had previously learned to play the piano when I was a teenager, so that might have made it easier. However the two are very different instruments. YMMV.

A lot of the difficulty in picking up a new instrument may just be lack of time. When I was a teenager I was spending 5+ hours a day playing the piano. I am not exaggerating in the least. As an adult it is very hard to find 30 minutes a day of time. It took me about 3 years to become very good at the piano. Another few years would probably have made me even better. This is consistent with the 10,000 hour rule. A naive calculation would conclude that it would take 30 years of practice at 30 min/day to become equally good at the guitar.