Why does the steering lock after driving through a puddle?

This is not uncommon and crosses most, if not all vehicle brands. If rainwater from under vehicle is allowed to splash onto drive the belt driving the hydraulic Power Steering pump, it can cause power steering belt slippage. Many newer vehicles are now using electric power steering pumps, which do not rob engine of horsepower, and as a byproduct, do not have any belt that can slip when wet.

A vehicle owner can verify that the drive belt is in good condition, the belt tensioner is functioning properly and that all orginal under carriage splash shields, are in place. (And SLOW DOWN in wet weather)