Just install Admin Tools's package on top of your existing installation, twice in a row, without uninstalling Admin Tools before or in between. This will refresh the files and copy any files which are possibly missing (didn't get copied in the first update attempt, or were accidentally deleted).
Tip: This trick applies to most, if not all, all Joomla components which use the standard Joomla extensions installer code.
Nicholas K. Dionysopoulos
Lead Developer and Director
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