Well, believe it or not, she didn't figure it out on her own. The tent thing. She phoned. "Hi, I'm back... and by the way, is that your guys' tent on my lower lawn?"
As I say, the previously posted exchange had been trivial little bits of larger e-mails about more pressing concerns. And the back-and-forth had concluded a full week before she flew home. While it had loomed large in my family's awareness, somehow it had slipped out of hers in the midst of goodbyes to other grandchildren, trans-Atlantic flights and jetlag.
But when I responded "Ah, well, yes, the tent ... that's where you're staying," she got it.
Oh my, she laughed. It was even better this way, because I got to hear her first reaction once she got the joke. She laughed so long and so hard I eventually pulled the phone away from my ear and had plenty time to answer my own kids' eager whispers "who IS that? is it grandma? did she see the tent?" I think she laughed all the harder because of her own obliviousness to the joke when she first saw it.