"What if" is an interesting one! I have so many bits of kit in pockets and on keyrings that I have very little I'd need in a knife tube. Many of the basics (fire, first aid, sharp, torch, signalling, cordage, simple tools) are covered by my wallet and keyring.
On the basis that the "what if" is not a full on **** scenario, it would be for a lost in the woods/hill overnight situation.
I suppose that the knife kit would be duplicates/spares of many of the things in my pockets, plus some additional bits such as:
- potassium permanganate (fire lighting, water treatment, wound wash & snow/water dye): local chemist, £1 or so for a small jar
- button compass: couple of pound on eBay
- water carrier (unlubed condom?): couple of pound from eBay
- tampon for tinder (NOT FOR 1st AID before anyone starts!): cheap own brand from any supermarket
- petroleum jelly in an appropriate container (fire lighting, chafing thighs!): any supermarket
- mid strength painkillers (4x 400mg Ibuprofen, anti-inflammatory as much as pain): pharmacy
- antihistamines (2x one a day, mild allergic reactions such as bee stings): supermarket
Can't think of much else, as my everyday carry is:
Belt (small krab with @3m of braided paracord lanyards)
- leatherman squirt
- LED Lenser P3
- MRT pager
Keyring
- CPR mask
- peanut lighter
- whistle
- encrypted USB copies of important docs
Wallet
- duct tape
- RAC membership card
- cash
- bank card
- drivers licence
Laptop rucksack
- tourniquet
- Israeli bandage
- vetrap self adhesive bandage
- fabric tape
- EMT shears
- surgical gloves
- small strobe (£10 jobbie from bushcraft show)
- petzel emergency headtorch
- Sharpie pen
- various medications
- Leatherman kick
- shemagh
- leather gloves
- hat
- spare glasses
- Cliff bar and other munchies
- long spoon
- pertex jacket in drybag
- Pebble backup battery for phone
- spare batteries for torch and pager
- spare house key
- bottle of water
- bright red raincover for rucksack
Watch
- compass
- altimeter
Before you laugh, I was close to the 7/7 bombing and stuck in central London having to walk quite a few miles to get out of town to my digs. It made me a bit paranoid!
And yes, I am trained in how to use the tourniquet!
Blimey, looking at that list I'm surprised at how much I carry to work every day!