Motherwell manager Stuart McCall has targeted Samson as a replacement for Darren Randolph, who will leave Fir Park at the end of the season, with Birmingham his expected destination.
Speaking after his side's goalless draw with Aberdeen, Lennon said: "We got correspondence from Motherwell yesterday and they are going to open up negotiations. He has been absolutely fantastic for us and we felt, for a club our size working within our budgets, that we made a good offer. Sammy has declined that and taken a bit of a gamble.
"He believes in his ability and let's see where it takes us. But he has been absolutely terrific, a top bloke. To see him coming in as number two to Paul Gallacher, then picking up the reins and getting into the Scotland set-up, and he could now be at the runners-up of the SPL. We will see where that one goes."
Lennon has already had a potential replacement in training in the form of Kyle Letheren, who left Kilmarnock last month, and said: "We had a look at him and he handled himself very well."
Samson showed why McCall is keen to sign him with an excellent first-half save from Joe Shaughnessy's header. St Mirren struggled to create chances with their best effort a 30-yard free-kick by Dougie Imrie, which was tipped over by Jamie Langfield.
The game ended in internal acrimony for St Mirren when Lennon took off substitute Lewis Guy, 18 minutes after the striker came on. The substitution is believed to have been sparked by an exchange of words with Lennon's assistant, Tommy Craig, who had berated the forward for his attempt to win a free-kick. Craig followed Guy down the tunnel after he came off for Jack Smith.
Lennon said: "There was a bit of disrespect there to one of my staff and I'm not having that. I'll not mention who it was to. We have a standard at this football club and that was certainly unacceptable. I think my actions showed you how disappointed I was in it."
The other major talking point was a disallowed goal by Aberdeen winger Jonny Hayes, who was flagged offside after running on to Niall McGinn's pass and slotting home in the 69th minute.
Aberdeen manager Derek McInnes said: "There's been an honest mistake by the official. I felt at the time he was onside and I've watched it again now a few times and it's clear he was played onside. It's frustrating, I thought we had enough good chances, certainly in the second half, to win the game."
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