SOLVED. Preteen's Mystery. Narrated by a Great Dane or some other big dog breed. Read around mid 2000's. Spoiler ahead. [s]

[Margie]

Could it be [Big Honey Dog]Curse of the Scarab? Cover matches, it's for preteens, and 1st in series is about missing puppies, but the dog's name is mentioned before the end.

[Kris]

Curse of the Scarab by H.Y. Hanna? Honey is a female Great Dane, dog detective.

Google search of Goodreads:
site:goodreads.com "middle grade" "dog detective"
then select the Images tab

I added some details to the header/ topic title. Feel free to edit it.

[Ffion]

Curious Incident of the Dog in the Nighttime

[Kris]

Can we eliminate Watchdog and the Coyotes (1995) by Bill Wallace? First person dog named Sweetie.

Google Books preview:
https://books.google.com/books?id=3Vj...

[Danielle]

McGrowl books by Bob Balaban or Hank the Cowdog come to mind.

[SamSpayedPI]

Beware Of Dog and The Original Adventures of Hank the Cowdog for Danielle's links (first in series).

[Kris]

Great! Glad we could help, 0.