lost passport/ urgent help

So my sisters passport got lost while in the care of a ffamily member. The passport contained the visa with the stamp and the I-94 inside it. Now when filling out the application I know they will put b2 visa as entry but how will they prove they came in on b2. Visa without no passport with visa or I-94????? I don't see the point In getting a lawyer because what can they really do about it? They can't magically make the documents appear. But I will be consulting with one hopefully tomorrow. But please any insight would be greatly appreciated

You need to put b2 visa as entry and leave the I-94 blank. Though the I-94 can prove you arrived here before the age of 16.

Bumpity. Bump.