No, I think it unlikely that Peter Randall would have filed a claim for the deaths of his two family members since they were not killed as part of Quantrill's August 1863 raid against Lawrence, Kansas. I think it was more likely that Peter himself suffered some form of damage at some point during Quantrill's raid which prompted him to file that claim.

Assuming the two Randalls and Hargrove were taken away and killed during the three final months of 1863, I examined what records I had of the region where they lived and draw a blank. This leaves me with two theories, one stronger than the other. Your Idaho connection gave us these additional clues. You gained from her the information that "In 1863...were forcibly taken from their homes by a band of marauders and carried several miles south of Blackwater Township where they were living and all three were murdered." There were no guerrilla bands active in the region around Blackwater Township, northwest Pettis County, during the last three months of 1863, although there were isolated acts of violence in the general region. This leaves me with the two theories:

Confederate Colonel Joseph Shelby's October 1863 raid was so fast that many of his men were inadvertently left behind or fell behind because of the rapid pace of his ride. I account for the great difficulty that these stragglers from his column faced against the Federal cavalry in the days after Shelby's raid passed south into Arkansas in Chapter 18 of my 1863 book. Away from the column these isolated groups were forced to subsist on the charity given them by farms they passed both for food for themselves and forage for their horses. It is conceivable that when such a group stopped for assistance in northwest Pettis County a southerner may have referred these battle-hardened troopers to go to his Randall neighbors in order to settle an old score, or that one of Shelby's men with those same feelings against the Randalls and Hargrove regarding some of their early war activities against their southern neighbors settled an old grudge. I think this is a long shot, but I have encountered some examples in Missouri's guerrilla war before. I also think it is likely that this "band of marauders" the lady in Idaho referred to may not have intended to get Hargrove, too, but simply found him at the Randalls, or vice versa. However, Shelby's troopers were not in the habit of killing Union soldiers, as Shelby was usually scrupulous that his men fight according to the accepted rules of war.

My more likely assumption is that a band of guerrillas making their way south to winter in Texas stopped by and captured the Randalls and Hargrove either because someone in their group knew of them or a southern neighbor sent them that way. This could explain why the "band of marauders" took these captives south of Blackwater Township before they killed them. Based on our research of the early war activities around Dunksburg, it seems that there were lots of men of strong enough northern sympathy to band together and fight against long odds in that area. Perhaps this "band of marauders" simply wanted to get themselves and their captives away from this neighborhood with all its northern men before they killed the prisoners. It was customary for the guerrillas of west-central Missouri to winter in the Sherman, Texas area, and they didn't all go at the same time. I have no specific reports that a group of guerrillas rode through this area on their way south, but the following spring I have documentation that one or more groups of guerrillas making their way back from their winter in Texas passed through this general area, and they killed several men as they travelled.

This is not very specific, but that is about all I can find to explain a "band of marauders" who carried off these three men and killed them some distance to the south during the last three months of 1863.

Bruce