L.B.
S/he went off for an adventure and got lost. You don't know if you will be able to find him/her or if s/he will be able to find his or her way home, and you hope s/he is okay. Emphasize to your daughter that this is why it is so important that your daughter stay near you and Daddy when you're out, and never go anywhere with anyone without asking your or Daddy first. (The "don't talk to strangers" rule doesn't work; they think of strangers as scary-looking people; dangerous people will not act scary but friendly or pretend to know their parents. Meanwhile, if your daughter gets lost and needs help, she needs to know the safest people to talk to - moms and dads with kids.)
Hope you find your dog!
L.