Dashboard is currently down for maintenance so apologies for not having screenshots:
It is almost definitive from looking at the mobile search events on the discovery dashboard (http://discovery.wmflabs.org/metrics/#mobile_events) that the data is inaccurate in some important way.
If you look at the desktop searches, they follow a common weekly pattern that match what we see in pageviews (drops on the weekends):
If you look at mobile web pageviews you see bumps on the weekends:
But the mobile web search dashboard does not show this pattern. This is very strange. We have also recently found a discrepancy between search event logging and pageview API counts, which suggest that at least one of our methods has an issue.