Christopher, it's not an oversight. When you change an LNAB (what we call the Last Name At Birth), because that is a component of the person's WikiTree ID, the way the software works is as if the original profile was merged with a new one.
If you write to info @ wikitree.com (without the spaces), they may be able to restore your original contributions, as well as other data that may have been lost as a result of the name change.