Fishing was not something Twilight had ever been too fond of. She could appreciate it from afar, but it was the kind of thing that required too much focus and too little activity at the same time. She needed something that kept her brain going, and while the sometimes slow wait of fishing did make for a good environment to think in peace, doing so would more often than not leave her too tangled in her own thoughts and distracted to pay proper attention when she was called to action again. In spite or maybe because of that, she couldn't help but draw similarities between fishing and what she was doing.
Both involved casting bait, occasionally waving it around, and waiting to see if something would bite. The main difference was that she herself was the bait in that instance. Or rather, her presence there was. The other difference was that it would be far harder to notice if something had bit down in time to catch them. But the unnerving wait was still there, that feeling of having to focus on nothing without being able to let herself get distracted.
At least she wasn't alone. She had guards all over the town, who'd gotten there before her, wearing civilian clothes. That would only help with spotting when and where something happened as soon as it did, alongside a decent idea of who was there. It wouldn't give definite answers on who the culprit was, unfortunately.
That was just the deal with coils. She could recognise something was the result of one by analysing it, but there was no way to spot any sort of connection between the effect and the user as something was happening, not that she'd found at least. Her guards would be able to see something was happening, but from there they'd just restrict the list of suspects, if things went well. A great improvement and a starting point, but not a solution. Still, enough to make the investigation manageable.
She wasn't expecting the target to act in broad daylight as ponies watched, of course. In fact, she was banking on them avoiding that. The previous time, they'd waited and found a spot where attention was low, and they would most likely do the same. That was why Twilight had her guards specifically keeping eyes on areas with less activity, places where it was reasonable for nopony to pass at times during the day. She had them hiding over rooftops or inside buildings, or simply wandering around.
She hoped her presence there would be enough to draw her target to action. She'd deliberately made a show of arriving to make sure her presence wouldn't slip past their attention, and the previous time it hadn't taken too long between her arrival and the next act of vandalism. Still the wait was unnerving, the inactivity she had to force herself in, just being there to lure her target into a false move but having to always remain alert.