I have a friend (well more an acquaintance) that is getting re-baptised. She said she wasn't ex'd but that her ward she was baptised in originally had lost her baptism records.

This sounds strange to me. Don't they have all those records at the COB? Or perhaps her baptism record never made to SLC all those years ago?

This does happen, though it is extremely rare in the US. When I was a missionary in Bolivia one of our baptisms was a rebaptism due to lost records.

This was an older family member. At 35 years old, decided to become active for a spouse (wrong reason to be Mormon!). There were no records of the small town baptism done in a local river. That person is now 80 something years old. The Mormon bunch could not find any record of the PH or baptism. This person had to start over and in the 60's, the LDS bunch was helpful to move him through the ranks to gain a Temple marriage. Yes, I have heard of this happening.

I can report the person never was able to find balance back in Mormonism. It was some sort of active, then inactive, then active, then Jack-mo....decades of the revolving door.

Too bad there was no support, Mormonism looked like the best option in those days for that Utah family member.