"Other" truck

I understand about 95% of what Isaac says (and he says a lot!). Partly this is because I know which sounds he can't pronounce, as well as which sounds he's likely to use as substitutions. But mostly it is because I spend so much time with him. Since I know nearly everything that has ever happened to him, I can use our shared experiences to help me deduce what his unclear words and phrases might mean.

This advantage was made clear to me after Isaac spent 30 or 40 minutes away from me today. Well, we were both in a children's shop, but while I was off in the shoe department trying to decide which sandals to buy him, he and my sister got to play with a variety of toy trucks. Isaac had a terrific time, and he tried to tell me about it afterward. At dinner, he said with excitement, "Two big truck. Big yellow truck! Bucket truck!" (You'll have to imagine him pronouncing truck as tluck to get the full toddler experience.)

"Oh," I said. "Did you and Aunt Erica play with a big yellow bucket truck at the store?"

"Yeah!" Isaac said. "Bucket truck. [Indistinct] truck!"

"Say it again," I said. "What kind of truck was the second truck?"

He immediately knew that I hadn't understood him, and his excitement evaporated. His forehead creased, and I could tell he was thinking hard. He tried again, using what sounded like the same word, but this time he was quieter and much less enthusiastic. He looked intently at me. In addition to trying to understand what he was saying, I tried to interpret what his expression meant. Mostly he looked like someone striving to remember the right word, like he was trying to solve a crossword puzzle clue that was just out of reach. Also, he looked expectant -- he was hopeful that I was about to figure it out. But he looked unhappy, too.

I still hadn't understood what kind of truck he was talking about, and he could tell. He didn't try again. He gave up, and defeatedly, perhaps even a little lamely, said, "... other truck" instead.

It took him a moment or two to shake off his failure, which seems alarmingly temperamentally similar to his parents. However, he did cheer up and tell me about the "big boy" who had also played with the trucks, so the story has a happy ending after all.

- - - - -

So, Erica, what was the "other" truck? Later on I tried to guess, but Isaac denied that it was any of the usual suspects: concrete, flatbed, dump, cherry picker, semi, pickup, delivery, etc. Besides, he knows how to pronounce all of those! What obscure truck have I never encountered before?