This is an odd one; to explain the steps and the result, I did roughly the following.

1.) I bid for 100 energy on the market with Crowns
2.) Once I won the bid, I used it with previous purchases to buy 50 Shining Fire (4*) from the Supply Depot
3.) I used the Fire to heat a clean (no mods) Strike Needle from L9 to L10 with 100% success
4.) I then purchased one Volcanic Iron from the Token Vendor in Haven with tokens
5.) I went to the Alchemy machine nearby in Haven, and I seem to remember left clicking the Strike Needle and it not being entered; no wonder, as it was equipped.
6.) I then unequipped it, and clicked again so it was inserted into the Blitz Needle Recipe, and crafted.
7.) The Blitz crafted, and generated a Unique Variant with 2 mods, Medium Slime and Low Gremlin
8.) I don't remember seeing the Strike Needle then, but I equipped the Blitz into Weapon Slot 2
9.) I then logged out, using the red X top right.
10.) Today when I log in, the Blitz Needle remains equipped... But the Strike Needle is back! And it's reverted to Level 9. The Shining Fire is gone though. I definitely only had one Strike Needle (item crafting is ridiculously long, expensive and grinding) and it must be a duplication of the one I was using due to it being heated to L9.