Slipped

He slipped the pen off the desk and into his pocket.

She slipped on the spilled drink and spilled her own drink.

The spy slipped the secret code into the message, without anyone realizing it.

The restaurant's popularity has slipped due to poor customer service.

The secret plan was slipped into a confidential memo, without anyone noticing.

The building's safety standards have slipped over the years due to lack of maintenance.

The spy slipped past the guard and entered the building undetected.