I have not found anything untoward regarding prayer blankets. For the most part, these are blankets made from yarn or fabric by women in a church who pray while making it for whoever will receive the blanket. In Catholic parishes, the completed blankets are placed on the altar during Mass on a specified day and blessed by a priest.
However, your mention of the blessing that came with the blanket that refers to placing it on a part of the body that needs prayer/healing made me suspicious especially because you also mentioned that these women are involved in Reiki and Healing Touch.
Sure enough, when I checked further, I uncovered a New Age energy-based version of the prayer blanket known as a "healing blanket" or an "Energy blanket" that is used by New Agers to do everything from cure disease to balance one's "chakra" (and all for the low, low price of $485).
The bottom line is that prayer blankets are a beautiful ministry, but the kind that are used to "heal" people are New Age.
If the note accompanying your blanket makes any claim other than to bring you comfort and peace via the prayers that were said while it was being made, I'd toss it in the trash.
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