Though I have never broken a mast (or even close) I was concerned about mast breakage down near the base on one of my earlier TI's. What I did was went to Home Depot and bought one of those Ames replacement ax handles (they are yellow plastic overmolded over a fiberglass pulltrusion) I took it home and stripped all the yellow plastic off the pulltrusion. I then slid it into a piece of PVC pipe and dropped it down into the bottom of the mast. The ax handle is around 32 inches long weighs about 1 lb and is super strong. You can put each end on bricks and a 250 lb guy can jump up and down in the center all day long ( I helped design the thing a long time ago, and built all the molds for it). If you see pictures of my TI I have one of these pulltrusions as my bow sprit, and also as a rotating mast topper (they are super strong and light weight).
The thing cost 14 bucks, won't corrode, and just slides down into the bottom of the mast (held down by gravity). Basically it just re-enforces the critical area of the mast giving it more strength. It doesn't change the way the mast flex's up above (I don't recommend trying to re-enforce the mast any higher than just the base), it's just an extra safety factor for your own piece of mind.
I have massive sails (260 sq ft) on my TI and have probably pushed my TI's more than anyone else out there, never with any issues or problems. On my latest TI (2012) I didn't bother dropping that pultrusion into the mast when I bought this latest boat, I don't feel I need it.
But if you want a little extra piece of mind, this is something you can do to set you own mind at ease. ( I suspect you had a faulty mast, since this is the first one any of us have heard of breaking this way), I'm sure Hobie will stand behind it warranty wise, they are the best in that way.
Thats is a great idea on the axe handle. I was looking for something like that to stick in the hull in case if it ever snaps again. I was thinking of a aluminum pipe about 4 ft long, but for the price, that's good enough.