Darn, I am so rushed to finish a Christmas present, was hoping to finish the weaving, twist the fringe and wet finish tonight so that it could hopefully be put in tomorrow's mail, and so of course I made a rookie mistake. I forgot that I have hemstitching at the beginning of the scarf, and failed to put in the hemstitching at the end of the scarf before cutting off the loom. I do have 4 picks of plain weave and then about 5 inches of ends for the fringe. Is it at all possible to hemstitch after the weaving is no longer under tension? I am really kicking myself. Thank you for any suggestions.

Twist the fringe on the end of the scarf that you have just cut off. Then remove the hemstitching from the beginning end of the scarf (very carefully and a bit at a time) and twist that end to match the other one. At least it will be the same on both ends and should be fine. I don’t hemstitch when I plan to twist a fringe anyway.

I know your post is a few months old and you have it figured out already, but just wanted to say, "Been there!". I like Jennifer's solution, but there is also the option of blue taping (painter's tape) the fringe to a surface and doing the same to the body of the scarf so that there is tension on both areas. A heavy book is another alternative. You can then hemstitch. It won't be as easy, fast, or as nice as when done on the loom, but it can work. Of course, this is one of those oversights you aren't likely to do again, but just in case. :)

Probably way too late to contribute, but if you follow Jennifer's excellent suggestion, you can avoid the to me unsightly pull apart of the warp by twisting the last thread of bout A with the first thread of bout B before you twist the fringe. Twist all bout A threads as you would normally. Same goes for bout B. Carry on with rest of the bouts in the same manner.
I've found this method a great method when the loom just has to be liberated.