The Civil War Day by Day; An Almanac, 1861-1865 by E. B. Long, p. 145, says a skirmish occurred at Whippoorwill Creek, KY on 12/01/1861.

Dyer's Compendium of the War of the Rebellion,Vol I, p. 730, shows skirmish at Whippoorwill Creek, KY, 12/01/1861, 26th KY Inf Reg.
Vol II, p. 1208
Unit organized at Owensboro, KY, July-Nov 1861, mustered in at Nashville, TN 03/05/1862. Saw action at Woodbury, KY 10/29/1861; Morgantown, KY 10/31/1861; moved to Calhoun, KY Nov 1861 and was there to Feb 1862; action at Whippoorwill Creek, KY 12/01/1861; moved to South Carrollton, then to Calhoun, Owensboro & Nashville, TN.
Reg lost during service 2 officers and 27 enlisted men killed and mortally wounded & 2 officers and 142 enlisted men by disease. Total 173.

The Union Army, Vol IV, p.336

26th KY Inf Reg recruited and organized by Col. Stephen G. Burbridge. Co's came from the Green River counties by men who knew everthing there was to know about that area, from Bowling Green to Henderson. This unit mustered in to Union service 03/05/1862 in Nashville, TN. No mention is made of Whippoorwill Creek, KY. Mustered out at Louisville, KY 07/10/1865.