If your friend was solo at the time then 90 days is legal & means nothing.
Reading between the lines, what's probably happened is he has flown when not current for insurance purposes. The group will be (rightly) concerned that the insurance company won't pay up.
My group's insurance company, for example, imposes a 90 day currency requirement. I could legally make a solo flight beyond this but the insurance company wouldn't pay up if I bent the plane.
Steve1234, your friend is in the very difficult position of having to either commit insurance fraud, or cough up for the damage from his own pocket (the group and possibly other third parties involved will probably have a claim against him for damages either from his negligence in bending the plane, or breach of contract). If it was me I would tell the truth as it has a habbit of coming out in the wash, and I wouldn't want to risk prosecution. "Oh what a tangled web we weave", and all that...
Not a nice position to be in at all, and just goes to show the importance of making sure you are current both legally and from an insurance perspective.