as far as I know, you are out of luck. Do you have a legacy store or a New Merchant Services account? If you have anything besides Merchant Starter, you can view "Click Trails" to show how many people have gone through your site, but thats about it. I have found this site useful for Yahoo Store related stuff as well. http://www.ytimes.info/resources.html If you do find out you can view the log files, PM me.
thought about it a little more and realized that there is a caveat. There are 2 ways to host a Yahoo store: 1) Though webhosting 2) Through the store If you use the webhosting side of the yahoo Merchant services for your store, you can view your access logs since your pages will contain your products. (If you use the dreamweaver extension or a HTML editor to add/delete/update your site, then you are using the webhosting side) however, If you use the store, (editing the stores contents through store manager) you will have to rely on clicktrails. Check out the MS manual, its actually pretty helpful in comparison to other gides yahoo has put out over the last few years. Quick thought, you may be able to add an include on the bottom of your page to create some sort of log.