My adventure guide listed a 405 trinket for completing the Engine of Innovation storyline (the one for Sparks of Ingenuity). I completed the storyline and received my final spark + In Tyr’s Footsteps achievement but I didn’t get my 405 trinket 
Anyone have any thoughts on what I might have missed?
I believe it represents an item that is possible to make with the spark, which I can see as being misleading. It mentions that they are used for crafting powerful items, but instead of showing one out of the many possible crafts they should direct people back to the crafting orders or profession area.
You basically just got the high end material. You can use it yourself or do a crafting order for a piece of gear. The pieces crafted with sparks are often pretty powerful for whatever level of content you’re doing as you can upgrade them. After the full questline you’ll have 5 sparks. I recommend researching what to craft as after this 5 they’re very rare.
Thank! I have all but one piece of Sparks crafted gear but I think you are right that the tooltip is confusing. It lists the 405 trinket as a reward, but then when I hover over it, it has yellow text at the top that says “sample item”. I’m certainly not going to waste a spark without confirmation of how this works, Blizz! 
By chance, does it show you the Alacritous Alchemist Stone?
Yeah, it does. Do you think this is just a misleading tooltip and it’s simply indicating I can get this crafted? Lol if so! I feel dumb
It’s indicating that you can get it crafted. Ngl though, Blizz kinda doing everyone dirty because I’m pretty sure that’s the trinket everyone sees 
Could have at least gone with Lariat or whatever weapon your spec uses.
It will also still show even after getting the fifth spark, as you’ll be getting more.
Ooooof I’m a dork! Thanks for helping me work it out!