If your MacBook came with Lion, as you indicate, then it will not be able to run Snow Leopard. How did you erase the hard drive? Is there still a recovery partition on the drive? To find out, restart the computer and hold down the command and R keys on your keyboard during the startup.
If it turns out you are able to boot to the recovery partition, make sure you are connected to the Internet and then do a software restore.
If you cannot use or cannot find the recovery partition, I would suggest carrying this in to an Apple store and asking for their assistance. Be sure to make an appointment first or you may spend a long time waiting to speak to a Mac Genius.
Best of luck.