I had a similar experience.   This picture was taken 3/2/06.   I covered up my strawberry plants for the winter.   When I uncovered them, I found a couple of heads of green leaf lettuce.   I had grown lettuce in this bed the year before and it obviously reseeded!   It was the best tasting lettuce, not bitter and it lasted for 3 family salads.   I can’t seem to grow it as well when I try.   J     This is just one head.

Nancy in Texas