Lost unique resource while upgrading spirits

[Baron01]

Hey everyone,
I have encountered what surely seems like a bug related to cultivating spirits. I used the wold spirit for a long time as I liked its passive bonus (getting slightly more focus on hit) but I wanted to try something new. This was partially because I did not want to upgrade the wolf to max as the resource require, Knot of Voidness, is scarce and I only had 1.

I decided to try Spearbone. Upgraded it to just below final upgrade when I noticed that my single Knot of Voidness disappeared from my inventory. I could upgrade Wolf spirit to max before but somewhere during the upgrade process of Spearbone the Knot of Voidness disappeared.
I was not used to upgrade the Wolf by mistake as it is still one below max upgrade either.

Anyone else experience this or similar issue with disappearing resources?

[SireChicken]

Upgrade 5 uses a Knot of Voidness on Spearbone

[rey-]

i have 2 spirits on max (currently at beginning of chapter 5) and still have enough knots for one more on max and maybe another one halfway through. Yes they are scarce, you "should" make up your mind on what you upgrade past the point of having to use Knots, but it is not that much of an issue, that you've just used your singular one.

[[GRVTS]Fat Bastard]

Don't worry bro you'll end up getting so many knot of voidness you'll be sick of it.