I hadn't gone far when I realised I'd left it in the kitchen, still plugged in to the charger; and I almost turned back to the house to get it. But then I thought, Well, I'm only going to be gone for a short while. It's not very likely that anyone's going to need to get in touch with me before I get back.
So I carried on into town. And although I wasn't without my phone for long, I noticed a couple of interesting things.
The first was how many times I found myself about to reach for it. It's become habitual for me - as I suspect for many of us - when I have a spare moment, to check my emails or my Twitter feed; to see if anyone's been trying to contact me. And even though my phone wasn't in my pocket, still something kept triggering that little internal prompt - I'll just look at my phone.
The second thing I noticed was how, as that prompt to check the screen was immediately followed each time by the realisation that I couldn't, the pattern of my thoughts began to change - and change in a way that felt oddly familiar. Without the constant interruption of the internet, my thoughts began to flow again.
The thing is, the ability to muse idly is pretty important for a writer, and it was disturbing to realise how little of it I've been doing lately. But the ability to just pause for a second and check my electronic communications had become a constant interruption to that stream of daydreaming, the little river of ideas that should run constantly in the background and into which we should be able to dip whenever our creativity becomes thirsty.
I'm making an effort now to diminish that habit - to remember that just because I can check the internet, doesn't mean I must. It'll still be there later. And as a result, I'm finding myself making contact with a way of being that I'd almost forgotten about.
The writer Jonathan Stroud has recently launched a campaign aimed at giving children Freedom to Think. Take a look; it's a very simple yet hugely important idea, and I'm entirely in favour of it. But the freedom to think - and the time and space in which to do it - is something that adults need, too. We need to allow ourselves to be bored.
John's Stinkbomb & Ketchup-Face series, illustrated by David Tazzyman, is published by OUP.