5 year old spelling test

Hi all! My son is in a STEM school it’s an amazing school and they strive to get our kids ahead of the game with learning.

How ever now that he is in kindergarten we had a bit of miscommunication. On Monday my son was out sick… I found out the words on his work sheet(HW) were part of a spelling test for Friday. He told me about it Thursday evening. The school sent a news letter about an assessment happening at the beginning of the month but no reminder & not exact details…. Long story short he got 7/12 right and he was the only one that didn’t get a reward. I’m just trying to not let the guilt eat me up he was so sad… what would you do in this case? TYSM