Just to clear things up a bit. At our church we often have funeral services for people who will be cremated. This is attended by all who knew the person and care enough to attend. The coffin is carried into and out of the church and then transported to the local crem., where a smaller, private (usually just family) service takes place and the coffin slides through the curtains, as has been said.
A bit later, if asked by the family, we bury the ashes in the churchyard with a very short, private service and the place is marked with an inscribed memorial stone, which is laid flat on the ground as opposed to standing at the head of a grave. I was pleased to discover why some stones are flat. Hope this helps.
Anyway, a coffin can always be dropped accidentally, but this must have been dreadful for the family at the time.