Hi Farooq,
As long as you have provided what they have asked for, it shouldn't be a problem. Your previous company was shut down, was not your fault, the evidence that you could have possibly present was your salary slip that you have provided them with the decent explanation that I see no problem at all.
How many years experience have you shown? In the worst case if they don't accept this as a credible document ( salary slip) in order to award you the points that you claimed for, they will only deduct the points for the period that hasn't been accepted. For example:
Based on assumptions lets just say
Points you claimed while lodging the application= 75
Number of years experience 2 years = 15
Incase they don't accept the salary slip period covered is 1.5 years = 10( points deduction)
So all in all, the points threshold for acceptance under this program is =
60 points, even if they don't award you the points for that particular period you still be fine
75-10= 65, as long as you have points 60 or above and you have shown a credible work experience of at least 6 months.
Please note that the above descriptive matter is just an illustration to solve your query and solely based on assumptions as I don't know your points and points distribution for the attributes.
I hope it solves your worries