There must have been a flaw in the glass since you got that car and it finally blew out on you when some sort of temperature differential somehow happened with the screen being warm and cold hitting it (moisture, fog??) This happened to a van my dad owned in the 80's. same thing. parked it at the end of a work day and found the rear glass all shattered the next day without any evidence of impact. A security guard was watching the cars all night. Find out what your insurance will do for you. Most of them are very helpful with windscreen reapirs and they usually try to minimize or avoid passing costs to glazing damage to the owner just for general safety reasons (they don't want their clients driving around with cracked up galzing......but this might apply most to the front windscreen glass though....

Chombi