The April 23, 1865 "Battle of Boggy Depot" was no where near Boggy Depot. Phillips' report to Bussey says 58 miles west-southwest of Ft Gibson which would be in the general vicinity of Slick in Creek County. Boggy Depot is 130 miles south-southwest of Ft Gibson. The Confederates attached had left Boggy Depot seven days earlier, April 16th, headed north. Phillips says the rivers were all high and could only be crossed "higher up" and he was closely watching his right (west) and had scouts all the way to the Cimarron (present Keystone Lake). In the ORs this is called "Skirmish on Snake Creek". There is currently a Snake Creek in that direction but not nearly 58 miles from Ft Gibson, being about between Beggs and Okmulgee.

The error in the date comes from Gen. Bussey's report which is apparently passing on info from Phillips' report but with a couple of major misstatements. Bussey's report to Pope is dated April 27th and says the engagement was "three days since" (i.e. the 24th). Bussey, writing from Ft Smith, says it occcurred 50 miles south. Bussey has is facts mixed up but is apparently speaking of this same encounter. In the ORs, this is called "Skirmish near Boggy Depot, Ind. Ter" though nothing in either report suggests it was near Boggy Depot, only that the men came from Boggy Depot.

Local lore says there was some sort of engagement near Boggy Depot but this April 23, 1865 event is not it. In 1864-65 the Union troops were making scouts deep into the southern Indian Territory but I can find no documentation for an engagement nearer to Boggy Depot than Perryville (near present McAlester).

OFFICIAL RECORDS: Series 1, vol 48, Part 1, pages 201-202
Col. W.A. Phillips to Brig Gen Cyrus Bussey, p.201
Brig Gen Cyrus Bussey to Maj Gen John Pope, p.202

http://ehistory.osu.edu/osu/sources/recordView.cfm?Content=101/0201