HELP?

I know that i'm more of a lurker here, than a regular poster, but you
good folks have helped me out many times--
This is a biggie !
Our pond began losing water this week at about two inches daily. ( pond
is 20'X8'X 28 inches deep.)
The pond has a hole in the poly-liner, we found it when we removed a
large stone that had been put in to hold our huge Iris plant against the
side of the pond. With the clear water, the stone was easy to spot. The
gal who made our veggie filter two months ago, had placed it there and
forgotten it, when she finished.

I frantically called her and she said NOT to drain it, she would come
and put a (Wet Patch) on it. I've never heard of a wet patch for a fish
pond !

She said that she has done it for other ponds, using (a swimming pool
patch compound) and that considering the smallness of the area to be
patched, the substance used, wouldn't harm my fish.

I'm scared to take this chance without checking with you all first. A
100 gallon stock tank is $136.00. I want a good fix, not a quick fix--
my fish are too precious to me.
Bette in Central OH