I can give you an experience that really speaks to your question. In Washington it is illegal to take pick or dig plantings from the sides of roads and freeways, etc. One year, following a clear cut of some timber, one field popped up with more Foxgloves than I had ever seen in my life. I have always noticed clearcuts bring Foxgloves but this one must have just been the most perfect environment for them. I did not even think, my car was pulled over, and I climbed up a steep little hill in a dress and heels, and just took in the glory of all the 5 to 7 foot stalks of lavender, purple and white flowers eye to eye with me. It felt like a corn field of flowers, and a special special act of nature. Again, I did not think. Before I knew it, I had 5 stalks in my arms, (biennials die in two years) I was brought back to down to earth by the sound of a car door. I went to edge of the hill, and there below me, was a Stater, with the fosters grants and the toothpick, just looking up at me,and there I stood, in a dress with armloads of flowers. At the sight of him, I just dropped those flowers like I had never seen them before. Removing the toothpick, He asked what I thought I was doing. I really was scared I was in some big trouble. I said "Well, I guess I was stealing flowers" He smiled, and said "I better keep you away from my wife, she comes home with dirt on her dress from stealing flowers too. Grab a couple extra for the missus, and I will let you off with a warning. However, this was private land, owned to farm timber. A daisy or Biennial is one thing, though technically it is against the law here and I could have been cited. But no, I would not go into a yard, foreclosed or not, and dig up plants. You sure could give the bank a call and ask tho.
