does this mean this is the first prime of this kind (GFN-15)?
In just seven days since you joined PG !
GFN-15 are not rare.
You can check PrimeGrid Primes by Project in PG home page.
For GFN-15, you have to choose (GFN32768) Generalized Fermat Pime Search n=32768 from the Sub-project dropdown list.
Note that 2^15 is 32768.
You can also sort the found primes by date of finding or by prime size.
Do come to AtP.
It's a very nice and friendly team.
And we have a forum area of our own: https://www.primegrid.com/forum_forum.php?id=50
"Accidit in puncto, quod non contingit in anno."
Something that does not occur in a year may, perchance, happen in a moment.