In Karl Stumpp's book The Emmigration from Germany to Russia in the Years 1763-1862 there is no Gerlock's shown. There is however some Gerlach's shown. And a Jaehrlich shown also.
I have also seen Jaehrlich in some church records.
But even though Karl Stumpp did not show any Gerlock's going to Russia it does not mean some did not go there. As there is a few names not shown in the book.
Well not much help I guess but spelling variations is something to think about.
Another book you should either get in at your local library or to buy would be a book done by Adam Giesinger called From Catherine to Khrushchev. This book covers everything else other than the families who went to Russia.