Some guy bought a pizza for 100000 btc in 2010, now a pizza is worth about 0.1 btc. How is that not deflationary? Bitcoins are limited and demand for them is continually growing due to privacy concerns, tax avoidance, media attention etc. Bitcoin being limited is what makes it deflationary unlike fiat currencies.
Because the price of btc increased between a time T1 and a time T2 does not make it "deflationary" as a permanent property.
If the oil supply drops to one barrel and the people of the world decide that this one barrel is worth everything every single person on the person ever owns, they will give the owner of that barrel the wealth of the entire world, which is in practical terms, infinite. I know that is still not absolutely infinite, and such a scenario is impossible, but it explains how a price has no limits.
As you said, it is impossible.