The only way he can try and get reimbursed for any repair bill he comes up with is by making a claim through his insurers who will then contact your insurers who will then contact you, at which point you state it wasn't you that caused the damage that he is claiming for.
Then sit back, relax and let justice take its course.
If, for some bizarre reason the insurers conclude it was you that caused the damage this simply appeal and demand they prove it