According to JazzDisco.org, specifically the 1951 Verve recordings page, "Undercover Girl Blues" was recorded on January 16th, 1951, and the personnel on the recording was:
- Saxophone: Lester Young
- Piano: John Lewis
- Bass: Gene Ramsey
- Drums: Jo Jones
My guess is that the information on JazzDisco.org is gleaned from The Complete Lester Young Studio Recordings on Verve, though I do not own that box set and thus cannot confirm. However, that site is general accurate in my experience, meaning that I have yet to find anything that doesn't match up with other sources while exploring it.