As much as the component kills it for me, I don't understand how Instant Summons has gotten so few downvotes. I would think the ability to prep one's valuables (SPELLBOOK FOR INSTANCE) to return to one's possession in the event of theft or other unforeseen separation sounds like a really wizardly thing to do. Afraid the gem will get stolen too? Stash it somewhere else.
Well, two things:
(1) In 5E, wizards are less spellbook-dependent than they used to be (compared to AD&D 2nd edition, anyway--I haven't played 3E or 4E) and spellbooks are relatively cheap to create. Making a backup spellbook doesn't take you six months of your life and thousands of gold pieces; nor do you absolutely need to have a spellbook all the time. In fact, you can feasibly even leave your spellbook at home for a whole weeklong adventure against orcs or something and manage just fine--you still get all your spell points/slots back every time you long rest.
(2) Drawmij's Instant Summons doesn't help that much if the spellbook
does get stolen. "Bohab the Tishabite has your spellbook; he is in Londonium" doesn't help all that much. It's
barely enough information to get you to the lowest level of scrying ("secondhand: have heard of the target"), which means the target will have +5 on its Wisdom saves, which basically means that you can probably scry out a mook after a couple of days of trying, but if the spellbook has already been passed to someone with a strong mind (high Wisdom save) you may
never be able to scry them out.
Especially if you don't have Scrying already prepared when your spellbooks with Scrying in it gets stolen.
Now, to be fair, that scenario only happens if Bohan the Tishbite happens to be holding or carrying your spellbook at the instant you crush the sapphire. If you cast the spell multiple times on your spellbook, you may have a dozen or more chances to recover the book--if the first sapphire doesn't get you the book, try again at midnight with another in case Bohab has set the spellbook down while he sleeps. (Perhaps that's why it's a ritual: so you can cast it over and over again on the same possessions.) Some DMs may give you grief about whether you can cast the spell multiple times on the same spellbook (citing "Combining Magical Effects" and the way spells like e.g. Bless do not stack with themselves for a higher bonus--they may claim that only one Drawmij's Instant Summons can be cast on the same object at a time) and for those DMs you're stuck with the base case of having to scry Bohab out, or at best hope to get lucky on your first and only sapphire.
TL;DR it's not absolutely horrible, and you've probably persuaded me to downvote it next time. But it's also not necessary
or that effective compared to just making a backup spellbook and storing
that where you would otherwise keep the sapphire. 10,000 gp of redundant sapphires buys a lot of backup spellbooks...