How do I get my latest commit back after it disappeared?

[RGVincent]

I had just commited my work to source tree to back up my changes for the day and I confirmed that the commit was successful and could see it on my source tree history.

but then I changed my working version to an older commit to find an older version of a file and now the commits ahve disappeared.

Is there a way to get this back or have I lost that work?