Charles Delaunay's biography of Django makes no specific reference to Les Lieber, but does cover Django's playing with the ATC (Air Transport Command) Band. "Django reached Paris sometime in October. He was immediately invited to play with the ATC band at the American base at Orly...Django took advantage of this band's presence in Paris to make some records, and was also featured at the Salle Pleyel in the first concert he had given for a year. The concert was relayed by the AFN, the BBC and the French national network". (This was in December 1945, just before Django and Stephane were reunited after the war.)
The Delaunay discography also lists the recordings but with Lieber shown as alto (although with an unexplained small circular diacritic - whistle?).
Les Lieber seem to be still playing as a quick search on "Les Lieber" will show.