Hi Ronnie -
I trudged to the library and looked in the "Report of the Adjutant General of the State of Illinois", vol. 1, pages 584-606 (1900 reprint of 1886 original). Those pages cover the 13th Illinois Infty., man-by-man. There was ONE casualty on 7 July, 1862: a man from Company A drowned.

In the "Record of Events" of Co. A, 8th Indiana Infty., is the following: "July 6-8.-- Resumed march, encamping on the west bank of the Cache River [i.e. on 6th]. July 7 marched five miles. Encamped on PEACH ORCHARD BLUFFS [emphasis added by me], scene of the skirmish of July 6. July 8 again marched five miles, passing through a small town with the name of Cotton Plant." (Supp. to the O.R., Janet Hewett et al., eds., 1995, Pt. 2, vol. 15, a.k.a. Serial No. 27, p.758). We know exactly where 8th Indiana was: Hill's Plantation / "Round Hill". Can't explain "skirmish of July 6" but likely it's a scriptographic / typographic error at some stage of copying & recopying.

What was the name of your diary writer? his company?

John