For other physicians, patients new to a practice were probably patients of a colleague previously. Most physicians are squeamish about 'raiding' a colleague's practice, and rightly so. Of course, we're talking about the common practice of purchasing a practice from a doctor who is retiring or moving. It can often be a smart way to enhance or refine a going concern, but if you buy a practice, you should make sure you get what you pay for. First, taking over a doctor's charts implies some responsibility to let the patients know where the charts are.
Many buyers leave it to the seller to do that, though.
If the seller does, it may just be a tiny ad in the public notices section of a newspaper's classified ad pages. No, if you're inclined actually to benefit from this transaction, I recommend taking the initiative by sending patients of record in the acquired practice at least two letters. And more are better. The buyer should prepare and mail the letters, but the seller should sign them. Yes, sign them all.