I started searching for a buck-boost controller and got distracted and thought "I'll get my bearings with parts.io by looking for a familiar part that parts.io has in its database." This was the Linear Tech LTC6957-3 clock buffer. I was surprised/confused/annoyed to find that there is no MSSOP version of this chip listed on parts.io, only SOIC. I knew that there was no such SOIC version of this chip. Then I looked closer and see that the SOIC part listed by parts.io is in fact the MSSOP-12 part. If you're looking to select a part for a crowded, small (i.e. cheap prototype) PCB you'll appreciate that SOIC != MSSOP/TSSOP, right?
A second case of this I hit a few days ago to mention in passing is that there are 0603 size Schottky diodes, but not according to parts.io (example: Comchip Technology CDBU0530). I spent a long time trying to find alternative package types that were at least similar to 0603, but didn't find anything. If I'm wrong about this, please enlighten me.
I'm enjoying the exploration of parts.io. More on that in a different category.