I am a Fire and Life Safety Inspector. I need to create floor plans where I can place the required elements (extinguishers, exit signs, hose cabinets, directioanl arrow, etc.) and send the .ai drawing to a sign shop to produce wall mounted Evacuation Plan signs. I am new to Illustrator and, despite my best attempts, relatively speaking, the objects either don't show on the drawing, or the sign shop gets an error that the objects can't be found.
Iwould ask them tospecify what kind of PDF file exactly they need (PDF/X? Which color profile?) and then save as a PDF according to their specifications. There will be everything inside the PDF. Also: make sure they print that using Adobe Acrobat.
You might have less trouble with them when the placed symbols are vector artwork. Should be possible to get that.
If that doesn't help, please show us screenshots that contain the Layers panel (the layers must be "open" so contents are visible)