they do remember each other, and us, for much longer than 3 days.
I had a little 5 week-old guy for 2 weeks in February 2017 here before I had to let him go to someone else since it was only chaos home with him and my 2 other males.
He came back 2 weeks in July while his owner was on vacation and I visited him some time in September again to pick a forgotten bowl up after my birds had been there while I was on vacation.
The then 9 month-old little guy jumped on me to say hello, which his owner said he never did with strangers, so he clearly remembered me as his "first mommy", although we only had 2 + 2 weeks of history together and he had spent most of his time with my birds, not me.
That has also happened with swallows I had taken care of at a wildlife hospital in UK, they recognized me after several days of not seing me, and came to me, which is something the staff had never seen wild birds doing.
And when my 2 budgies escaped and I found them back after 3 and 4 days, they recognized both me and each other, as do all my birds when I leave them in someone else's care for 2 or 3 weeks in the Summer. They clearly recognize me when they see me again and show how happy they are.
It has also been proven that singing birds give "names" to their kids, each of them has a distinct sound that the parents use only for them. In my opinion, this implies much deeper bonds than people used to think small birds are able to, and we should not underestimate the trauma and sorrow we submit them to when we separate them from their friends and mates.