Yes the TD/staff secure the bagged chips until play resumes. For some tournaments this may be for a week or more. Think of an evidence bag that the police use to secure evidence from a crime scene. We've seen all the TV shows where the evidence is brought out in a lab and the sealed bag is cut into to release the contents. This is the type of bag used and it's next to impossible to 'spill' once sealed.
Typically this is the procedure I have experienced
When play has ended, staff will come to a table and process each player in turn.
Players chips are counted, player & staff confirm the amount
Staff fills out a tag that goes inside the bag
The chips are placed into the bag by staff
Staff seals the bag and ensures it is closed
Player is given a receipt with chip count
Staff collects the bags and stores them away from the tournament area.
When play resumes, the player presents the receipt and an ID (usually players card)
Dealer confirms the player and is allowed to open the bag when it is time.
