I have had bags turn up late on a couple of ST flights with BA (I use it alot!). The bags have always been delivered, albeit late, and I have never had a claim refused/not refunded.
One of the pitfalls of travelling standby is that the bags are kept on the Pan until the end of loading and sometimes get forgotten/missed.
Don't get me started on some of the charter companies 'third party' claims agents!
I don't think the whole story is here either.