Lost Receipt For Item Needing To Be Returned

I bought a printer for my son for college.  We didn't open it or hook it up until we got there.  Took it out of the box, set it up but he didn't print on it until he needed to print an assignment.  After setting up his room we took all the boxes and through them away.  The printer eats the paper and I took it back into the store to see what they could do and they said with no box or receipt I couldn't return it but it definitely was not working properly. They said I could call a numbere and get a duplicate receipt for a lost one and then will be able to return it.  Can you give me the number to call?