How does one paste text in a drawn text box?

Every time I right click to paste text into the text box that I just drew, the text box disappears!! I see the cursor in the box for typing text inside it but how do you paste copied text into it?

Seems you tried to use a form control of type TextBox. Is this what you did? If so, why?
Shapes of text-box type should accept pasted text. However, they only support a rather prmitive version of text, but very few of the formatting and none of the specific content elements you probably had copied.

A Text Box will disappear if text is not added; right-clicking inside it takes the focus away from the cursor so the text box disappears. A workaround is to add any text, even a space, before right-clicking and pasting. You could, instead, use the menu to paste without having to ad any text first.

A Text Box is a drawing object and, as Lupp says,

they only support a rather prmitive version of text, but very few of the formatting and none of the specific content elements you probably had copied.

You are better to use a frame, Insert > Frame > Frame interactively. A frame looks like a text box but can have columns, be linked to other frames, text within it can have applied styles, and it can include graphics. See Inserting, Editing and Linking Frames or there is more on frames in the Writer Guide in Documentation. Cheers, Al

More precisely, a frame creates a secondary text flow just like the main document context in the main text flow. It is a kind of embedded short sub-document (limited to the frame rectangle) where everything you can do in the main text is available.

right-clicking inside it takes the focus away from the cursor so the text box disappears

… which is definitely a bug.