bike crash

Hi, I've had a deja-vu bike crash, as in, it's happened to me before. I
was going downhill, and I went through a dip in the road I wasn't
expecting, which made my hands slip from the handlebars. This leaves me
still riding, but with my hips on the handlebars and my torso and head next
to the front wheel. From this position, I try to get up and I can't, and I
end up going down on purpose (for example this time I noticed I was headed
for the curb). I was wondering if I'm doing something wrong? Has this
happened to anyone else?
Ok, apart from the obvious... I had lost my glasses, was getting new ones,
and I was told they were ready the next day. But this could happen to
anyone with 20/20 vision as well, if they are caught by surprise. I am
about 20/60. I was scanning ahead to plot a line for a turn.