You haven't lost it. You've inadvertently hidden it. Happens regularly.
Hiding/unhiding panels is actually a "feature" of the software but is obviously never used because a) no-one can find it - there's no indication of its existence in the Lightroom UI, b) those who do hide their panels (usually accidentally) usually come here in a panic thinking their software is corrupt.
Right click any panel on the right hand side (where the Basic panel should be) then left click the word Basic to UN-hide it.