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Oil tends to go one of three directions to escape the engine.
1) Old-fashioned leak - You sound as if you've ruled out that possibility given the lack of oil spots below the car. I would also get under the car with a light and see if you have oil all over the underside. The chances of a catastrophic blow (as would coat the bottom of the car) that would leave no oil to drip later are minimal, but it is worth looking at.
2) Into the combustion chamber - This happens a coupla ways.
A) Valve stem oil seals, causing a slow leak that generates a puff of smoke at start or when taking off after idling a bit
B) Blown head gasket/s, causing a lot of smoke and a miss. You would know this fairly quickly as the engine would run like crap.
C) Blown ring/s, piston/s, connecting rod/s allowing oil blowby from the crankcase into the combustion chamber. This is indicated by smoke coming out of the tailpipe and the engine running like crap.
3) Venting into the cooling system somehow - Usually the cooling system operates at higher pressures than the oil circulation system causing coolant to get into the oil. The car responds by overheating, running like crap, etc. Your oil would not be empty, and would look like.... vanilla icre cream and chocolate ice cream melted and mixed together. Yes, it's a rather non-technical description, but it's the most accurate way I can describe it.
On to the noise - minor tick is usually a lifter, rocker, or valve issue (all related assemblies) and is not good, but not devastating. A knock is usually a broken connecting rod (the rod what the piston is mounted to and connects to the crankshaft). This is devastating news.
Frankly, your engine oil had to go somewhere. Most of the directions it would escape in cause smoke from the tailpipe. The ones that don't cause oil spots on the ground. I am very interested to hear how this turns outs and would like to know where your oil went.
As to driving it, it's your car, bro, and your pocketbook. Overall, you probably will need a new mill. Catastrophic engine loss combined with lots of ugly racket usually spell out death for auto engines. However, what you call a lot of racket may not be a lot of racket by my standards. A good mechanic that you can trust is your best buddy here. If the trip isn't far, and isn't through dangerous territory )(ie somewhere you'd not want to break down), then you likely won't hurt anything more by dumping in oil and taking it easy.
I have a Ford Aerostar with a cracked head. Said crack allows coolant to enter into the combustion chamber when the engine is hot. When I go out to start it, it fires up as soon as you hit the key. It doesn't eat oil at all, and so long as I keep the coolant level low, it doesn't really eat coolant either. It just won't start when hot and has power issues. I don't drive the vehicle unless I have to, and only when I know I won't be taking somewhere rough, but it still hauls me around whenever I need it, perfectly reliably cracked head and all. It will not last, this much is plain, but the point I'm making is that ugly engine problems can sometimes show only minor clues, and can leave the vehicle running okay for quite some time. The crack in my Ford has been there for a long while now (it's not worth the money to buy a fresh head, and definitely not worth the labor. When it dies, it dies).
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