I almost fix the carpet too! It was that damn Hydrocotyle sibthorpioides and it's crazy veins. As I was trimming the carpet, I thought I saw a loose HC Cuba stem so I picked at it. Usually it IS a Cuba stem and I just pat down the carpet after the trim, but no, not this time.
A gentle pull and off it went, along with a few mat of HC Cuba. If you look closely at the second picture, you can see the white vein. I hated how stems of Hydrocotyle sibthorpioides would pop up in the middle of the lawn. Blast you inferno Hydrocotyle sibthorpioides!