I wouldn't think the exchange rate would change much in one day. Check all transactions and see if something is missing. I think PayPal has one set exchange rate for the day, but it could be possible they have one rate for selling dollars and one for buying dollars and you will lose money on a round trip.
Have you checked your bank account, are you sure money wasnt trasnferred there?
PayPal sometimes acts strange, after dispute and refund I had my money frozen and couldnt do anything, they fixed it by transferring my money back to my account, however after that out of nowhere I had negative PayPal balance, something like ~1$ minus, I wrote them about it and they promised to fix it.
They simply deducted that ~1$ from my account, thats how they fixed it :D
Instead they should have sent me that amount of money and not take it from me ;)
Close, I just worked out the missing $1.02 was the PayPal fee for what I sold, also on eBay its nearly $3 fee there as well. Seeing that they are the same company I don't see why I got charged from both of them. (they already rip me off massively with currency conversion.
I still cant work out what happened to the refund, I contacted the seller and the money is gone from his account. I checked my bank like someone suggested and its not there either, still no reply from PayPal.
If the payment you have been refunded was payed by a debt or credit card it will go straight to your bank but it will take up to 10 days to show up while pay pal gamble it to make interest of your money on the stock exchange. To check this click on details next to the refund amount on the left. Only refunds that show up instantly are ones payed by credit in your pay pal account, any bank transfer or instant payment used from a Bank account, debt card or credit card go straight to your bank account in 7 odd days usually.