Maybe
SK = Strange Key (which I have in inventory)
But don't know what to do with it, or where to use it; nor with the additional number from clue.
Got to go for 15 mins, but I'll continue when I'm back. Leave me a hint if you can make progress.
I'm back, any progress 
Found another hint
in his office
for which we could use the number clue.
But I don't know what
MASK refers to
Found numbers
on bench in park
Yay, used phone
with the number from bench in park
Found hidden passage and door with number code.
And play alone AGAIN 
And out 