I agree, it shouldn't be a problem. If you've loosened the tensioner center bolt, you should be able to rotate the tensioner by grabbing the idler wheel and pulling it toward the slack position, which will also push the adjusting nut up into the hole again somewhat.

When you first loosened the center nut and backed off the adjuster nut, did the tensioner body rotate back on its own as it released tension on the roller? If not, the tensioner may be kaput!

Gary