The graft is probably either below the soil level or very smooth so you can't see it. The red leaves will be coming from the scion (the top part of the tree which is grafted onto the rootstock) and the green from the rootstock. A green leaved rootstock can't produced both green and red leaves and nor can a red leaved scion. You could dig out suckers and provided they have some roots they should grow. However, red leaved shoots coming from the scion will probably not have any roots.

Rhizo, that's terrible! I would have flipped out if someone came onto my property and tried to steal anything from it. Especially my plants! You should have whipped out your cell phone, snapped a picture and put it on social media. That would have "shamed' them, like you said you wanted. OP, I would absolutely squee if somebody stopped at my house and asked about anything I've planted. A delivery guy who brought us some drywall last week commented that he really liked the teal color of our living room, and that he liked everything we've done with the house since he last saw it a few years ago.. I love those sorts of compliments. It always feels good when someone tells you they like something you've done. It especially felt good because I had personally picked out the Maxi Teal, and had campaigned for it to dh for weeks. He thought it was going to be too dark. So it's always funny when someone compliments the color. lol I always look over at him and lightly smirk.

Well, actually it probably will be fruitful - it's just a gamble as to whether or not it's something you'd want. Most of the clonal apple rootstocks were selected for size limitation or disease resistance - not for fruit quality; seedling apples (standard rootstock) will be quite variable in habit, size, and fruit size/quality/ripening period. I've seen some rootstock shoots from under ornamental crabs that produced some pretty good apples - looked like they could have been seedlings of Golden Delicious.

Many ornamental crabs are grafted or budded, so if that is a sprout from the root system of the original tree, there's a possibility that it won't be the same as the original, it will be whatever the understock was/is. If it is a seedling, it definitely won't be the same, unless the original tree was a species that comes true. Have I confused you enough? If a seedling, easy to move. If a root sprout, it will be attached to a root of the original tree, and possibly a fairly large one, but you won't know until you start digging. It can still be dug, but it will be harder to get enough roots so failure is a little more likely, and recovery will be slower. I've dug root sprouts, about 75% success rate, seedlings, close to 100%. YMMV. Whether seedling or root sprout, it still will be part of the original.