Stan Lee wasn't playing Stan Lee (the famous and noted comic writer) in this particular cameo, he was just playing the part of "a man".
“Here’s something a bit more interesting,” Sparr said. She held out a fax. “Possible gamma sickness. Milwaukee. A man drank one of those guarana sodas. Guess it had a little more kick than he was looking for.”
“Where was the soda bottled?” Ross asked.
Phase One: The Incredible Hulk - Official Junior Novelisation
As such, his presence wasn't especially notable or coincidental
It might interest you to know that in the original script, the character who drank the poisoned bottle was just "A MOM", making her part the ideal stand-in for Stan Lee's cameo since it would save them having to create a new set and pay for five speaking extras just for a one-line joke.
INT. KITCHEN - MIDDLE AMERICA - MORNING - WEEKS LATER
A MOM is making a chaotic lunch for a bunch of seven year olds on
a playdate. Whole thing one camera shot: moving around, staying
with her, back and forth from fridge to table: a plate of apple
slices to get em started…popping the tops off some bottles of
juice and handing them around, stops to take a swig of her own
soda bottle sitting on the counter (we might know that bottle if
we got a close look at it, but we probably don't)… a plate of
chicken fingers and as they're dropped off we see some kids are
drinking… back for something to dip em in…
Incredible Hulk - Edward Norton First Draft Screenplay (05-13-07)