I'm the proud owner of the snapped rudder that nohuhu alluded to in his post.
I had the rental guy tell me I hit something
In that case, have your rental guy call me...or refer him to the pictures in my post. If you (or I) had hit something, I concede there would have been the possibility for something to break, but I think that would have caused damage to the twist and stow mechanism or the front of the fin. This sort of damage in this case is obviously caused by a lateral load (i.e., the force of the water on the deflected rudder) snapping the fin, not by something striking it head on. If you had indeed hit something hard enough to break the rudder, you'd also surmise there would be some accompanying damage on the centerboard.
To carry over from that other post there's some discussion on why these rudders snapped where they did
When I went in to my dealer today, he gave me a loaner part to use for a while until my replacement TI rudder comes in. What I didn't realize is that the TI-specific rudder (part number 88991185 "rudder assy / TI blade") is different from the "large sailing rudder" - part number 81397001. I'm interested to see if the boat will be at all manageable with the smaller rudder installed - has anyone tested this? I'm skeptical, but it should be fun to try.
More importantly, after getting the temporary rudder replacement in hand, a visual comparison of the two is somewhat telling regarding why the TI's may be more prone to the type of failure now experienced by at least two of us. Shown below are the TI rudder (top) and the large sailing rudder on the bottom.
What I hadn't realized prior to comparing the two is (A) just how much of the TI rudder's surface area is forward of its pivot point (probably aiding reducing the forces needed to turn the rudder), and (B) how "skinny" the rudder is at exactly the point where mine snapped. There are a lot of lateral forces (and some torque, as well) being applied to a very small cross-sectional area there.