Should the employer be informed about a worker seen taking out company goods and giving them to another person, with no witnesses other than the observer himself?

Whoever sees a Muslim’s property being stolen or damaged must rescue it, especially if they are entrusted with it. They must also forbid the one committing the evil. As for the money that has already been stolen, you must order the thief to return what they took or its value, or to seek permission from the rightful owner. If they refuse, then inform the rightful owner so they may claim their right. The absence of witnesses does not prevent you from informing them, unless you strongly suspect that the usurper will deny it, and the rightful owner will believe the usurper and disbelieve you.