As a Canadian who was raised on British English, I seamlessly switch between British and American English when interacting with clients from the US, England, and Canada. This flexibility in language is quite natural to me. Furthermore, for someone who meticulously conceals their identity, adapting in such a manner would likely be effortless and unremarkable.
"gotten" would be less unusual for a Scottish person, although it is usually used in the context of "ill-gotten [gains]" it does crop up now and again outwith that.
Cheerio, Later, Take care eh?