1. press the STAT button
2. place the cursor on the list which is at most to the left (in your case probably L2)
3. press 2ND DEL = INS + ENTER
4. a new list is created and you are prompted to label the new list
5. 2ND 1 = L1 + ENTER
if you have a big portion of luck all your datas are present. Even if you delete a list in the STAT screen it is not removed from memory.