I totally feel for you.. I understand your dilemna perfectly. the same thing happened to me, I had huge classes where I didn't really know my professors beyond office hours. I did get to know one of my younger professors though, because i took a smaller chem summer class with her, and the following semester she helped me in o chem. So there was one letter. Then the second, i had no idea. I did have a very good letter from a calculus professor. I simply assumed calc to be close enough to a science that it would count. Nope..Schools would call me to say my file was incomplete because i didnt have that second science. LECOM even told me that all i needed to do was to have some professor write some formality letter with no more than a sentence and it would count. To me this is absolute BS, because i think a good calc (or stats in your case) letter should count more than the stupid formality letter. So, what I did was to write to schools an official business type letter stating why i did not have a second science letter (huge classes, told by my advisor that calc would count, etc..) and that i wanted the calculus letter to count for the second science letter. I said I felt it better represented me and a letter of formality was just that. Surprisingly, most schools accepted this letter and said it was okay to use a calc letter. The only school that didnt was LECOM, but screw them. I sent the letter to: Western, PCOM, Touro, Ohio, and it worked. So if you do this, there is precedent that it has been done. Just make the letter very business like and official, and the admissions committee will probably accept it, if you have other good letters. Send me a pm if you actually want a copy of the letter, i can attach it to email and send it to you if you think it would help. Good luck.
connor