I had wiped my 2010 macbook air and had tried to reinstall the os in recovery mode but the message "this item is temporarily unavailable" keeps popping up as I try to install os lion. Can anyone help me out ??
That's a weird issue, your best bet is probably to download the "OS X Recovery Disk Assistant" to reinstall OS Lion.
From Apple's website:
"To create an external OS X Recovery, download the OS X Recovery Disk Assistant application. Insert an external drive, launch the OS X Recovery Disk Assistant, select the drive where you would like to install, and follow the on screen instructions.
When the OS X Recovery Disk Assistant completes, the new partition will not be visible in the Finder or Disk Utility. To access OS X Recovery, reboot the computer while holding the Option key. Select Recovery HD from the Startup Manager. "
Note: In order to create an external OS X Recovery using the OS X Recovery Assistant, your Mac must have an existing Recovery HD, which in your case it most likely already does.