What's to know about a rose tag? They tried to make the transplants seem more important by putting a serial number and possibly the name on the tag. Still do they same thing with plastic these days. And of course, when the person planted it, off came the tag and onto the dirt. I have found several. Rose tag, key to master padlock, old roadster. Cool roadster. Can't figure out what rock thingy you asked about, but would love to see it close up.
Ditto on the other hobby advice. Dig long and prosper.