I finally got back to Spectrail and passed the cumulative points achievement. While my score does show more than the 10K required points it's not showing in my achievements and I haven't received the Sterling plushie. In terms of importance this isn't high comparatively, but if there's some spare time I'd appreciate a look into this. Thanks!
Your achievements show that you do have over 10,000 points for the cumulative achievement, as you've stated on your post. However, the plushie is the prize for a higher tier (20,000 points).