It doesn't sound as if you really did 'resize' your image....it may appear so, but in reality you didn't.
I'm guessing you used the IMAGE > Image Size dialog to change the 'size'......and also by changing the 'resolution'.
If you really want to re-sample the image you need to make sure that the re-sample option is checked when you do.
The 'resolution' of a digital image is nothing more than data written to the header of the image....it has no bearing on the image size whatsoever.....but, having said that it IS a factor used when re-sampling.
You mention image size in inches....this is not the image dimensions...its the PRINT dimensions.
In other words, with the amount of pixels in your image, and at the resolution set by you, you would (if you printed it out on paper) get a printed image of those dimensions.
With 're-sample' turned OFF you can use the 'resolution' setting to denote the size of PRINT you will get.
With 're-sample' turned ON you will re-sample the image (add or remove pixels) to or from the image which will indeed re-size it.
In a nut-shell, if the image you are working on is only ever going to be viewed on a digital device then ignore any 'linear' measurement.....digital images are defined by their pixel dimensions....which, as a side note, is not the images' resolution.
My guess would be that when you 're-sized' your image 're-sample' was unchecked, and the measurements your are reading are the PRINT size.
Its an easy mistake to make as that dialog is not very informative as to just what is going on.
Regards.
MrToM.