Strange text message

My phone was charging and my mom was getting to go get dinner when I received a text from her. I thought it was strange for her to text me when she could have just come and told me what she wanted. I looked at the text from my lock screen and it was a weird text that looked like it was quoted from something because of the way it was worded and the fact that it had quotation marks. I unlocked my phone and went the Messages app the text was gone and the only texts that were there were the ones between my mom and me. Has anybody else experienced this? I only wish I had taken a secreenshot of the text before I unlocked my phone, but how was I supposed to know that the text would disappear when I unlocked my phone?