I started a lengthy text, put my phone down and forgot to send it. I would like to retrieve that text is there anyway I can?

If it isn’t in the message list in the messages app it is gone. Messages that are being composed are not saved in storage, only in RAM, and if the RAM is needed for another app the space holding the draft will be “reappropriated”. If you are going to not complete it in one sitting you can select and copy the text, then paste it back later.

I’ve done that. This has sometimes worked for me. Open Messages and try to start a new message to that person. Or open your previous thread of messages to that person. For me, at least, this will often bring up what I typed previously. Good luck.