Build-A-Bear Workshop’s “Pay Your Age Day” promotion came to a quick and unfortunate end last Thursday as stores were swamped with massive crowds. Although the one-day promotion was only announced on Monday, word spread quickly. When Thursday morning rolled around, many stores had lines wrapped around the block before they even opened.

In order to take advantage of the promotion, parents had to register as a member of the Build-A-Bear awards club, providing an email address. Once enrolled, they could theoretically buy any bear in the store for as many dollars (or pounds) as their child’s age. Build-A-Bear stuffed animals can normally cost around $25. However, massive lines prevented many parents from even getting near the stores.

Stores had to begin turning people away for safety reasons, and in some locations, authorities even closed stores. Angry parents across the United States, Canada, and the U.K. have taken to social media to berate Build-A-Bear. To try to make up for the failure, the company handed out vouchers to the guests who had to be turned away. A statement on the company’s website reads:

It is our sincere desire for all of our guests to enjoy the best Build-A-Bear experience possible. As such, our goal with the voucher extension is to enable us to better flow traffic to the stores over the next several weeks to avoid long lines and wait times as much as possible. Therefore, we strongly encourage guests to consider delaying their next planned trip to Build-A-Bear, and we appreciate everyone’s understanding and patience in this matter

The event was created as a kickoff for the chain’s new “Count Your Candles” program, which allows kids 14 and under to get the “Birthday Treat Bear” for the cost of their age when purchased during their birthday month. Company CEO Sharon Brice John stated that there was no way for them to have estimated the kind of crowds. They saw the campaign succeeding on social media and put a notice out announcing that they thought the lines would be long, but it was “beyond anything we couldn’t ever imagined.”

There are many marketing takeaways from this campaign. Don’t underestimate the power of social media. Have a “Plan B” ready in case your campaign is so good that it goes viral. Have a system in place for rapid crisis communication. And perhaps even more importantly, use campaign mistakes to reiterate your love for customers and your brand identity. Build-A-Bear has done this well by offering everyone a $15 voucher towards the purchase of a bear, which is creating earned media buzz and a potential flood of new customers.