I saw this last Sunday on a sign.

Problem:
A possessive apostrophe is missing.

Explanation:
I saw a magnetic sign attached to a pickup truck last Sunday.

The sign’s title was “Mobile Mikes Tile Service”, with no apostrophe anywhere, and there was contact and other information beneath the title.

Nothing on the sign implied that there was more than one person named Mike, so I assume that there is just one “Mike” who runs the business.

Oddly, although many sign makers make the mistake of inserting an apostrophe where it does not belong, this sign’s maker omitted an apostrophe where it did belong.

Solution:
“Mobile Mike’s Tile Service”