Respectfully, I disagree.
Perhaps thats the conclusion he came to after not only searching for Barbara himself and finding no sign of her, but the SAR teams also not finding her, nothing to do with what she was wearing or what she was drinking.
Putting it simply, Barbara was not found, so therefore she is no longer where he thought she was - his conclusion is reasonable IMO.
I suppose the question is, would RT still come to the same conclusion (of abduction) if Barbara was wearing jeans and a Tshirt, carrying a bottle of water? IMO, the answer would be yes.