On the tool bar on the left hand side of the screen. The same place that your selection arrow is situated.
(There seems to be a million checks points and when a solution is offered they expect you to know how to navigate to the hidden menu sub menu)
The tool icon this looks like a square with arrows on each of its sides.
Double click this icon (Tool Icon)
It brings up a menu window.
Hit the reset tool button.
This should bring back your tool controls.
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You can also reset your workspace as this may also be causing you issues. That is located on the top right hand corner of your Maya window it says workspaces next to it. There is a drop down menu click reset workspaces and it will bring your workspace back on track.
Im new to Maya and I have been having this problem all the Fing time. Im not writing this to solve the original problem as Im sure in the last 12 years this person has solved it. This is for the noobs that are coming on here looking to solve the same issue. Hope this helps, sorry for being so long winded but I needed an explanation like this myself.