The contents of the pouch have not been specified in the question.
Assuming a complete set of 100 tiles, including two blanks and a standard Scrabble set of letters, the following answer is given.
There are 4 S’s in a standard set. Since 3 tiles have been removed: M, U, I, There are 97 tiles remaining, the probability of drawing an S is 4/97 on the first draw and 3/96 on the second draw. The probability of these being consecutive draws with no other tiles drawn is (4/97)(3/96)=1/776=0.001289 approx, 0.13% approx.