Thank goodness your Poppy is ok.
I'm not a fan of these harnesses, they are too similar to a horse halter (I"m an ex horse person) and horses can take those off really easily. I'd look at a harness like this,
Best Pet Supplies Dog Harness in Burning Orange @ pet care live dot com (note I just randomly googled a picture of that harness, I have no idea what this site is about otherwise, they just had a good pic). That's what I use, if it doesn't fit perfectly then they can get out of it, but if it fits perfectly there is no way out of this one because there is fabric holding it in place, whereas a twist could get them out of the nylon one easily because they are so small.