Actually it's simulating as intended. When using #b13 you should only really use ASCII transmit mode during simulation, you will see the error described if you use raw mode and enter invalid values for the mode (e.g. typing 2<send> in raw mode.).
That is because the special # mode is only ever intended for ascii character input (in the real chip too), so only ascii number characters "0-"9" (48-57) are ever valid entry. This mode also specifically needs a non-number ascii character to finish input, so in ascii mode you must enter something like '42x'. If in raw mode you use 2<send> then you are immediately terminating the ascii entry, hence the value 0 is received.
In raw mode you will need to use the raw ascii values 48-57 only, followed by a different number, e.g 48,49,32. This is confusing to do, so ascii mode would be easier to use.
Entering any other raw number will give an invalid input to the serial buffer, hence a 0 received.