There are a few possible explanations:
* Misremembered title: Perhaps you're thinking of a different poem by Carroll.
* Misattributed poem: It's possible the poem you're looking for was written by someone else and mistakenly attributed to Carroll.
* Imaginary poem: It's also possible the poem doesn't exist at all, and you've dreamt it up or heard it from someone else.
If you can remember any details about the poem, such as:
* Lines from the poem
* The overall theme or subject
* Where you heard it
I might be able to help you find the poem you're looking for!