Very possible that Gardai gave the number (despite data protection)! I know of cases of this happening in the past. Very strange that they couldn't simply phone you rather than text you...geez :-(
Ring them back and get them to explain themselves. Perhaps they took down the wrong number.
It could well be a scam phishing for personal details, the text looks for insurance details, with which they would get name & address and a hook to start with, for instance they could then call the insurance company pretending to be their customer and advising, say, their new email address, oh and I've misplaced my insurance doc can you send me on a copy, and now they have your date of birth as well.......and so on....
The thing to always wonder is does this make sense, the text doesn't say where this allegedly occurred, doesn't ask why they left the scene, if someone scraped your car would you just send them a one line text ? (Even apart from the guards giving a number to a third party). In my view if it's weird, it's probably a scam and don't touch it