Was the account just deleted? This can be undone on the Admin panel under "Manage Users" (using your Admin account). However, if data for the account was actually purged (permanently deleted) then there is no recovery that I am aware of. This is how disk is recovered for new use. Separate disk backups of the data would be way to have permanently, ongoing, data recovery outside of Galaxy.
Sorry if this is bad news. If some from our admin community read this and have other advice, they are welcome to post!
Jen, Galaxy team