When you use Explorer, do you see a folder called USA&Canada? If so, that is the map folder. Leave it.
If not, you said you were copying files using Home. I assume you were using Home's backup facility. It's much better to use Explorer and ensure hidden folders/files are showing.
Anyway, in Home, Tools-->Preferences-->Folder preferences, it shows where it will store the backup files. The default is: C:\Documents and Settings\yourname\My Documents\TomTom\HOME\Backup\GO\Backup01
Look there and see if the USA&Canada map got put there.
If so, check that not only the folder is there but there are a bunch of files in the folder.
If so, I'd suggest this......use Explorer to remove all the loose files from the root of your unit, NO folders or their contents.
Now, connect your unit to the computer. Start Home. Home should say that the application (firmware) is missing and offer to download and install. Accept that. Then copy back the map folder.
BUT..........................
You are eligible for the Latest Map Guarantee. Did you already do that? If so, then the map is on your computer! Likely in this location:
C:\Documents and Settings\yourname\My Documents\TomTom\HOME\Downloads\complete.
SO............
You said Home doesn't see a map in Contents but is that contents of my unit? Check the icon for Items on My Computer. You should see a map listed. So you can select it to be installed.
In summary...........
The map may indeed be removed from your unit but it may very well be on the computer, particularly if you did the Latest Map guarantee, then it WILL be on your computer.
If you did not do the Latest Map Guarantee, then call support at 866-486-6866 and explain your situation; they'll add the map to your account to download.
And some files from the operating system may be missing from the unit. Mind you, if you are getting the 'no map found', then maybe they are still there.
I'd try restoring the map, either from the computer or via a download after calling TomTom.
Good luck.