Whatever happened happened!!! This whole season has proven to me that they can not change the past. Every action that has been taken by the 1977 losties has proven to be exactly what needs to have happened to produce the future they came from.
With that said, at some point in the past the statue was standing in all it's glory but then it was reduced to a single 4 toed foot. My theory is that Jack and gang will try their best to detonate the bomb but in so doing cause many of the island mysteries: Distant past - cause destruction of the statue Less Distant past - cause wreck of the Black Rock 1977 - cause the incident which in turn causes the downing of Flight 815
Well, the good news is that my theory will be busted or verified by next week.