Am i obliged to buy when seller refused at first..

According to Audiogon rules, yes, you are obliged to buy for 48 hours, the offer is declined, or counteroffer made when making an offer. Offline contact with the seller/buyer has no bearing on the official offer. Sort of like things said off the record and on the record.

You should have replied to his e-mail and ask him to decline the offer immediately if he refused it in the email. That's life in the Audiogon jungle.

I see this is very recent. Maybe there is still time for you to Message him to work out the sale.

I contacted the seller and he said he already sold it the next day.