[Kromm]

In brief:

• Partial surprise is used when:
  
  
  1. Two hostile parties are moving blind to one another and suddenly encounter each other, leading to a hasty encounter battle. This is likely when the two parties are patrolling or searching, and through blind luck step out from concealment and run into each other at engagement range. For this, roll initiative and follow the rules under Partial Surprise.
     
     
  2. One party successfully sneaks up on another party that was expecting trouble. This is normally the result of winning a Quick Contest of Camouflage, Shadowing, Stealth, or similar vs. the prey's Per score or Observation skill. Don't roll for initiative! The Quick Contest above replaces the initiative roll, and victory at sneaking automatically gives the initiative to the sneaky party. The surprised party is affected as described under Partial Surprise.*
  
  
• Total surprise is used when one party successfully sneaks up on another party that wasn't expecting trouble. The dice rolls work like the second case above, except that winning the Quick Contest means the surprised party is affected as noted under Total Surprise.

* This is the case that applies in the OP.