As it happens expensive glassware destined for the covenant's laboratories was stolen before reaching it. Investigation revealed the presence of a Leper-Magus who not only seemed to implicated in the theft but tried to have the magus investigating murdered (through mundane means).
My question is, would it be a violation of the Code to use magic (Geomantia) to discover the location of the glassware, knowing that it is likely to be in the presence of a fellow magi?
I'd say no, as long as the spell only targets the lab goods... and only your lab goods. i.e. if you use a spell that reveals the presence of any/all lab goods... then you could have grounds for some theoretical complaint. If it targets only your goods, and doesn't reveal anything else about the area or who is there etc. Then I'd say you are divining into 'your own' affairs, since they are rightfully yours.
Also, the magus that might be targeted is in a very poor position to press anything at tribunal regarding you scrying on him as stealing your lab equipment could certainly be taken as an attempt to deprive you of your magic.
Although, as per usual, legal and illegal is decided by who has the votes. If the other guy is vastly more popular at tribunal than you, then you have trouble, no matter how naughty he has been.
Oh they used mundane means to find the glassware (deduction and a keen nose) but it's inside the "sort-of" sanctum of the Leper Magus and he's a bit too scary; although they're prepared to stand up to him anyway.
It's the opening gambit of the Unwilling King story seed from HoH:S. The Leper-Magus is a member of a Cabal (The Cabal of the Rosy Lance) formed to provide political support and expertise for the completely unpolitical magi of the Covenant of Rosalyn.
He's supposed to choose the lab-rat Bonisagi as his "beloved rival" but he's so impressed by how the magi stand up for each other and genuinely seem to care for one another, even when they need not or should not, he might just declare that status with all of them. They're just so precious! 
So far he's stolen the Bonisagi's glassware, accidentally sunk a ship owned by House Mercere, tricked the Bonisagi into killing a treacherous agent for him, teased the other magi at the covenant about their inexperience, used an AC to the covenant's smith (given as alms) to steal some of their metal work (which they've yet to discover) and challenged the Bonisagi into a contest for the glass ("Any contest; take your pick")...
The Bonisagi has decided to spend a season preparing for the contest but I don't think his 'beloved' is going to wait that long... Hmm what mischief can I get up to?
I am pretty sure that a magus who transgresses the code becomes himself 'outside the code' and is thus not protected by its provisions. So, by depriving a magus of his magic, in this case you leper mage stealing lab gear, he probably isnt protected by the provisions against scrying. This, of course, assumes you are able to prove the point at tibunal.
On the flip side, you can never be sure about these things until they come to tribunal, and when that happens it often has more to do political dimensions than a true and fair reflection of the code.
On the point about when it is scrying on the magus because you are targetting goods in his possession rather than the magus directly, that I think is quite clear. You are forbidden from scrying on the apprentices and even some covenfolk under this provision if it is to reveal information about a magus, so I have always come down on the side that this kind of legal jiggery-pokery was never gonna hold any water.
Not if they don't get caught. 
According to the principle of forfeit immunity described in the Guernicus chapter of True Lineages, I would say no. But Your Mileage May Vary.
In my opinion, forfeit immunity basically says, if you act like a jerk, then you can't hide behind the Code to escape the consequences.
Imagine for a moment the magus who took your glassware tried to complain at Tribunal. "I stole this guy's glassware and then he scried on me to get it back! Boo-hoo!" Even dressed up in fancy words and with better presentation, I really don't think that argument would fly. Especially not in front of a Tribunal full of magi who don't want their own glassware stolen.