I recently shopped at my drugstore and was disappointed that the best bargains were out of stock. I had waited until the last day of the sale week, and other clever shoppers had cleared out the bargains.

For those new to the shopping scene, a rain check is a type of IOU, usually from a grocery store, that, ideally, entitles you get in the near future an item currently out of stock for the same price it was advertised for during the time it was unavailable to you. (There are some exceptions, as when a circular or ad states that such an item was being sold in limited quantities.

If I were shopping at a grocery store, it would have been simple to request a rain check. However, the best drugstore deals generally involve a sale price, coupon and an automatic rebate. These deals seemed too complicated for a rain check, so I didn't even ask about one. Since then, I have learned how we can avoid missing savings on drugstore sale/rebate items when they are out of stock.

If you find yourself in a similar situation at your grocery store, simply ask the store personnel whether they offer rain checks or substitutions. They are not likely to offer these options, so you need to ask. Most customer-service counters at grocery stores even have preprinted forms. When you get your rain check, save any coupons you had planned to use with the sale-priced item.

If the rain check has a long expiration date, you may have time to accumulate more coupons for the item before you buy it to save even more money.

Requesting one can be more complicated at drugstores like CVS and Walgreens, which have rebates and/or Extra Buck rewards for featured items. To learn how shoppers should handle these situations, I contacted CVS headquarters and visited the Walgreens Web site to verify compensation policies for out-of-stock sale items.

CVS responded in writing, and the news was good. Store managers can either substitute a similar product and reduce the price by the amount of the Extra Buck reward, or issue a rain check. The manager would reduce the price by the value of the Extra Buck reward.

When I discussed the situation with my CVS manager, he said they prefer to issue a substitution immediately. Therefore, by knowing the policy and asking about product substitutions or rain checks, shoppers can benefit from weekly promotions even if the store is out of stock. And you may prefer the substituted brand more than the sale item!

The Walgreens Web site has its policy posted online. In response to the question, "Do you offer rain checks?" their answer is, "Yes, we offer rain checks for sale-priced items featured in the Weekly Ad that are out-of-stock. Rain checks are good for in-store purchases only and valid for 30 days. They cannot be issued or redeemed online. In some instances, a store employee may authorize the substitution of a similar item of the same brand at the advertised price."

Stephanie Nelson shares her savings tips as a regular contributor on ABC News' "Good Morning America." You can find more of her savings tips in her book "The Greatest Secrets of the Coupon Mom" and on her website at www.couponmom.com. She can be reached at shoppingmom@unitedmedia.com.