Just today I installed a program ClipMon
I've been running it sandboxed (sandboxie).
Gave a google search for "prag-2.swp" & nothing popped up - except for this thread.
Figured I'd search my disk for ".swp".
Everything tells me, "C:\CLIPMON\history\textclips\prag-2.swp.txt".
So perhaps CHKDSK found something that it did not like with "prag-2.swp" (inconsistent or whatever) & "cleaned it up". You happened to catch that.
Should be some record of it in Event Viewer.