The layout of the search bar in MobileFrontend is quite radically different from the one in normal operation. I'm not sure if this is intentional or not.
This is what it looks like when is unsupported or failed for some reason (e.g. network timeout for one of the JS requests when on a tablet). The search bar and button are completely invisible. They exist but have no outline or placeholder or anything.
It seems like both scenarios should result in the same rendering, and the search bar should be made wider. There's also no reason to omit the placeholder attribute in no-js mode. We don't do that in desktop either.
Successful page load by comparison:
The only difference between JS and nonJS is the primary button on the right side.