There is no way to know without using it. Not all checked bags get the high-intensity scans, and you have no way of knowing what did and what did not. If it got the high-intensity scan, your lead bag did no good - the film is ruined completely. I guess it would not hurt to try it, but I'd hate to trust it to any shots I wanted to keep. You could test a throwaway roll from the batch - if it comes out fine, then the rest should be good as well.
For what it may be worth - for anyone reading this - I keep beating this drum but I guess no one listens. 1) No lead bag will protect film from the scanners used for checked baggage. 2) Screeners and the TSA (USA) recommend against using lead bags for carryon baggage. If they detect the lead bag, they'll require you to remove the film and they'll rescan it without the bag anyway. Go to the TSA (
www.tsa.gov) website and see for yourself. 3) All film is damaged by x-rays, always. However, most film under ISO 800 can withstand at least 5 passes through typical US carryon scanners before damage becomes evident.
You can request hand inspection of film in US airports - they may or may not comply, but I am told that they mostly do these days. If you fear x-ray damage, that is the way to go. Lead bags are beyond useless and should not even be sold anymore - they are not recommended for the purpose they were made by the US government.
Anyway, end of mild rant - srtiwari - sorry that your film got accidentally checked and I hope it is ok - nothing personal intended, I'm just doing my usual grumpy PSA.
Best Regards,
Bill Mattocks