If anyone is thinking of making anything up, don't do it b/c schools *might* find out.
But if you're just worried since you did something but do not have a good contact name for it, don't worry. I did a lot with Habitat for Humanity in college. At first I did the whole sign up thing and went out to job sites, but then I discovered that there was a warehouse where they worked most saturdays prefab-ing stuff for the job sites. This was WAAY cooler to me since I grew up working construction for my dad. They had all the power tools, etc., in the warehouse and it was basically like a gigantic woodshop. So I spent a fair amount of time there, and it was my most enjoyable volunteer experience of college. But, like I said, I never signed up to go there, so Habitat had no record of me ever being there. As for the people running the warehouse, they were often different people. The only one I ever got to know what this old man who was always there. He sort of ran it more than the others. Well, he saw like 100 new people a week and never remembered my name. He got it right like half the time. I did not even have his contact info, and there was no way he could verify anything for AMCAS. So I listed my Habitat work and said right in my application that I had no contact information that was of any value. I gave the number of the Habitat central office for the city I was in.