For those interested in this (thus far) unsolvable question, I have just expanded an old blog post and converted it to a page, In which battle was Alexander McGruder/Magruder captured? I have waffled on this, but am currently leaning toward Worcester, 3 Sept 1651.
All names are now searchable! Many thanks to Marie McGruder for help with transcription. I’ve also added new detail about division of the enslaved by the Weems-Bowie family, and improved navigation within the page. Have a look!