Found a live wire hanging over a puddle in my backyard, glad I looked before stepping in

Had almost the same thing happen a couple summers back. I was digging up a shrub that died and my shovel clipped something that felt like cable. Pulled back the mulch and there was a length of Romex running to nothing, just buried a few inches down with the end cut and no cap on it. The previous owners here did all kinds of half finished projects and that was one of them. I flicked a non contact tester near it before going anywhere close and it lit right up, so it was live for who knows how long, right thru two winters of snow melt. I coaxed it back toward the house, followed it into the garage, and found it was spliced into a garage circuit with just wire nuts and no box behind the drywall. That part made me more nervous than the outdoor end honestly.

Mine got sorted when I had an electrician out for a panel upgrade anyway. He pulled the splice back to the box, capped it, and told me he finds dead landscape lighting and shed feeds left hot all the time, ussually from DIY renos in the 90s. Yours sounds like the same era of shortcut. The flip flop detail hit home. I do all my yard work in old sneakers too and never once thought about what was under the grass until that shovel moment.

We bought a flipped house a few years back and the crew that did the work left abandoned wiring everywhere. When I pulled out a rotted trellis on the patio I found a pair of wires stubbed off inside the brick pillar, both ends just twisted togehter with no cap. One of them was still hot off a garage circuit, wich the electrician later confirmed when he came out. My take is a little different from capping things and leaving them in place. Around here the damp gets into everything, and I have seen tape jobs turn to mush after one winter outside. So I had the electrician disconnect it at the panel and pull the whole run back out rather than leave a dead leg buried in masonry.

Cost me maybe an hour of his time and now there is nothing back there to find in ten years. If the wire serves nothing, out it goes.

Same era of shortcuts at my place too, except mine was inside. Pulled out an old wall-mounted radio intercom during a kitchen demo and the wire feeding it was still hot off a lighting circuit. Cut the power at the panel, put a proper wire nut and cover on it, and left a note taped to the panel saying where it was so the electrician coud find it fast. Curious how much your guy charges just to cap something like that, mine lumped it in with a bigger job and I never got a straight number.

Gonna push back on trusting that non contact tester alone in your situation. Those pen testers miss live stuff all the time, especally with damp soil or mulch between you and the conductor. Lucky for you it lit up, but if the battery was weak or the angle was wrong you'd have been leaning on that shovel with confidence. I test with somthing that actually makes contact before I beleive a wire is dead, or I just kill the breaker and confirm. Also surprised your Romex survived buried like that at all, the jacket on mine that sat in wet dirt for a few years was chalky and cracked when I finally dug it out.