USCIS cannot locate petition?

[SA123 0]

US citizen here. A petition I submitted for my parents is pending since April 2018. Since June 2018, the USCIS webpage says the case is ready to be scheduled for interview, but I haven’t heard anything since. 

 

I called to inquire about my parents’ EAD, which had not come in the mail and supposedly had already arrived, and I was told that the USCIS customer service representative’s computer didn’t have any information about where my parents’ petitions were. I was also told she didn’t know in which office the application was. I’m a bit concerned about this, and I’m unsure what to do. The automatic phone information also says that USCIS cannot provide information about the petition at this time, or something like that. 

 

Have any of you you had a similar experience, where a petition could not be found in the system? Do you know what had happened, and did the petition turn out fine? Thank you.