How can I download the Lion installation file?
Recovery options for Macs with Lion pre-installed are documented in HT4718:


Recovery HD: recovery partition on hard drive, accessible by booting with Cmd-R pressed til the Apple logo is displayed
Internet Recovery: If you got a new (empty) hard drive, your Mac will boot into an internet recovery mode


Recovery in both cases requires internet connectivity.

You can use this to your benefit by rebooting your Mac into recovery and connect a USB drive. Go through the steps to link your Apple ID to that Mac for a Lion reinstall. Choose the external drive for the install. You should be able to catch the process at a reboot and save the 10.7.2 installer for later. Worst case is you miss it and the system deleted the installer application. Just open the App Store and hold option when selecting Purchased. You can generally re-download things once the store knows you get a copy of Lion.