Scaremongering.
You are - and remain - a lawful permanent resident, until you file an I-407 (which you won't) or an immigration judge issues you a final order of removal (which isn't going to happen while you are on vacation).
You have a valid I-551 stamp, as proof of that permanent residence, and which is sufficient for boarding a carrier to, and re-entering, the US. (note, with a stamp, you often have to have a quick visit to secondary, this is nothing to worry about).
They took your card, because it has expired, and the extension letter doesn't extend it any more - my card expired ten years ago, so even though I got an(other) extension last year, it doesn't work with my expired card, because it's too old, which is why I also have to get a stamp every year.
The retaining of expired cards when getting stamps is nothing new, nothing to do with the current administration and nothing to do with your status. Those of us who have been posting here a long time, will know that retaining/shredding the card in front of you has been a common thing for years by many officers when getting a stamp. Not all officers, but many.
The fearmongering by, frankly, idiots, is out of control, to the extent even I was/am getting spooked by it. If I believed half of my friends, family and the media, next time I visit a USCIS facility I'll be detained by masked ICE operatives, and deported to El Salvador as a suspected member of MS-13, despite being as white as 1980s UK dog poop. Funnily enough, when I visited for a stamp recently, that didn't happen, because I'm a lawful permanent resident.
Don't buy into the scaremongering or let it negatively. affect you or your life. And get a better lawyer.