Can i claim itc on a gst invoice not bearing my gstin?

yes u can make the claim but your claim will not be permitted unless supplier put the proper invoice details in gstr 1

What do you mean by proper detail? He would not have noted my company name or GSTIN at time of purchase. 

FYI, I am not an Accountat or CA, just a business owner.

you can edit your gstr 2b by entering above detail in gatr 2.....and ask supplier to accept the same....you will get the provisional credit immidiatelly ....if supplier accept the request than all is good...if supplier rejects the same than you have to pay credit taken with interest....
if you have regular business with supplier than he will accept, otherwise it is hard to say anything

Yes I agreed to Mr CA Akhilesh Kumar Kandpal Sir...

@ Cyrus.,
Exactly said Mr Akhilesh. It's mean The supplier can't return invoice wise details. He is made consolidated return. So, He can't include your GSTN.
In the case of you enter received details also the supplier ll be accepted then no more issue. If not, He can't accept your reply then You can pay the tax at the bill amount......

Also a small convince you ll be discuss to the Supplier.....

If the seller does not accept my invoice then will it be treated as a invalid invoice and will I have to pay GST rate on top of the invoice amount which already includes the GST. 

What will happen in this case?

1. will it be treated as unregistered vendor spending and I will have to pay GST on top of final invoice amount (which already includes GST)?
2. or will I just lose the input credit but  not have to pay GST on invoice amount as is the case with unregistered vendors.

Is it better to adjust this in petty cash? As I understand Rs. 5000 per day at company level is the limit for petty cash that does not attract GST. That makes it almost 1.5lakh per month of petty cash supply that I can spend without worrying about GST..

if supplier rejects you request than the amount which you have taken credit will be included in your output liability with the interest amount.....