The adjuster probably just threw out a WAG. Until he went back and processed the info and put together an estimate, he wouldn't have hard numbers.
However, even if the estimate to repair was $4000+, it's probably a total and you will get a check for the book value of the car, which is apparently less in this case.
At any rate, call your claims rep and politely inquire about what's going on. Even if it's a total they shouldn't have taken the car until you agreed to either 1) accept full book value and they take the car or 2) accept book value minus salvage value and you keep the car.
JMO

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1983 M-B 240D-Gone too.
1976 M-B 300D-Departed.

"Good" is the worst enemy of "Great".