Can't access hard drive. Help please!

Question

I have a MacBook Pro that used Lion. The computer's software crashed and wouldn't start up, so I took it to my local Apple repair store to get it fixed. They said they could pull all my files and data from  my computer, since the hard drive was fine, and that they would reinstall it on my hard drive when they reset my computer. When I got my computer back and when through the initial set up and start up steps, I selected the option to retrieve data from a disk on my computer. My computer spent seven hours just searching for the disk, so I finally decided to ignore the data that's supposedly located somewhere on my computer, and just set the machine up again.
I set up my computer and realized that the Apple repair store reset or reinstalled Snow Leopard instead of Lion. I'm not sure how much a difference the OS makes, but now Migration Assistant can't find the other disk in my hard drive that has all my old data on it.
I'm in a country that doesn't have actual Apple stores or Apple support systems in place, so it'd be great if someone could help me! This post isn't very clear because I couldn't quite tell what the repair people did, so feel free to ask questions to elucidate some of my more confusing or inaccurate statements.

Answer 1

Reinstall Lion:
Reinstalling Lion Without Erasing the Drive
Boot to the Recovery HD: Restart the computer and after the chime press and hold down the COMMAND and R keys until the menu screen appears. Alterhatively, restart the computer and after the chime press and hold down the OPTION key until the boot manager screen appears. Select the Recovery HD and click on the downward pointing arrow button.
Repair the Hard Drive and Permissions: Upon startup select Disk Utility from the main menu. Repair the Hard Drive and Permissions as follows.
When the recovery menu appears select Disk Utility. After DU loads select your hard drive entry (mfgr.'s ID and drive size) from the the left side list.  In the DU status area you will see an entry for the S.M.A.R.T. status of the hard drive.  If it does not say "Verified" then the hard drive is failing or failed. (SMART status is not reported on external Firewire or USB drives.) If the drive is "Verified" then select your OS X volume from the list on the left (sub-entry below the drive entry,) click on the First Aid tab, then click on the Repair Disk button. If DU reports any errors that have been fixed, then re-run Repair Disk until no errors are reported. If no errors are reported click on the Repair Permissions button. Wait until the operation completes, then quit DU and return to the main menu.
Reinstall Lion: Select Reinstall Lion and click on the Continue button.
Note: You can also re-download the Lion installer by opening the App Store application. Hold down the OPTION key and click on the Purchases icon in the toolbar. You should now see an active Install button to the right of your Lion purchase entry. There are situations in which this will not work. For example, if you are already booted into the Lion you originally purchased with your Apple ID or if an instance of the Lion installer is located anywhere on your computer.
If the above isn't possible because the Recovery HD is no longer there, then you can go to the App Store and re-download Lion (if you purchased it on the App Store.) You will first need to update Snow Leopard to 10.6.8 by installing Mac OS X 10.6.8 Update Combo v1.1.
I suspect your files are simply on the drive, not on another drive unless they repartitioned the drive and put your files on the new partition. But if they just put your files back on the hard drive there is no need to use Migration Assistant.