Hi - welcome to the GMB. Like you, I've tried various sources and drawn a blank in finding any reference indicating this mark is related to Miroslav Havel, and I think you're going to need to contact one of the large Irish museums who hold collections of Waterford glass.
Waterford Crystal are no more, as you probably know, and even the visitor centre has ceased, I think. I could be wrong, but I'm not aware that this question has surfaced previously on the GMB.
First thoughts are that, if your story is correct, then this large upper case S looks unusually obtrusive for an artist's mark or whatever - such things are more discreet and often placed on a less obvious area of the glass. It might also be thought that Waterford would have been proud enough of this bowl to include their acid backstamp showing the factory name, which they did on almost all of their glass at that time.
I notice you say that your benefactor comments "Special Pieces that he made i believe he Signed S." - which sounds less than 100% convincing, possibly.
There are known instances of manufacturers incorporating a letter s on certain pieces of their glass ........ the mark =s= can be found on some Stuart pieces when they were owned by Stonier of Liverpool, but I've a feeling that generally an S in some form or another has in the past indicated a seconds. Apparently it's often difficult to see why a piece should be relegated to that status.
The design of this bowl, with the very noticeably graduated relief diamonds, does appear more of a C20 piece in its cutting, rather than something from Waterford, say 100 - 150 years earlier.
However, despite my comments your piece may well be from the Master, and would be great if it was.
If you do contact the museums, we'd be very interested to hear the outcome, and wish you the best of luck