I (almost) invariably buy petrol, mars bars, fizzy drinks etc on a card. I bet Cummings does too.
If unexpectedly away from work, at the very least I (or someone) phones to say so, and when I hope to be back. If I was a workoholic I would be making calls to deputy/ies so that the world didn't come to a halt without me.
I wouldn't disappear without saying where I was, or people might start looking for me. Even more so if I was Chief Adviser to the Prime Minister.
My phone and credit cards would be tracking me.
The card would show not only where and when I filled up, but also, importantly, how much I spent, which is a proxy for the fuel, and this the distance I had travelled. Could I have any reason for wanting to conceal it?
And I could show them, if they supported my story.
If not, however.....