To further comment on the points Shreve raised...

I agree it was very confusing for the audience to see the baby removed from the car and then see two caskets in the funeral scene afterward.

My guess -and I hate to say this- was that it was sloppiness on the part of the production crew, who likely realized their error too late and hoped no one would notice! I'd love to know if they got letters when the episode was originally aired!

Within the context of the STORY, however, there IS a possible logical explanation: Namely that the bad guys removed the baby before Tubbs and the rest of the Vice squad arrived on the scene, so the Vice cops believed the baby was in that car. And who likely arranged the funeral? Not the bad guys -they'd already left/been killed, so they weren't talking!! The vice squad would have arranged the funeral, and all of them witnessed the car blowing up with the occupant(s) inside. So they would've requested two caskets.

Of course, you'd think forensics would've hunted for remains and become suspicious that they only found the remains of one adult...but maybe forensics didn't bother when they had the word of an entire Vice squad as witnesses. Or maybe the blast was at such close range that it destroyed all human remains.

Hope this helps solve the mystery!

-Creative Type