After years doing this and working with 100s of very experience investors, we've found that hangups (sellers who call and hangup) can be some of your best leads. We recommend calling them 4 times in a row. Never leave a voice mail message. After time attempts calling, let rest for a week and do again. This can be a huge money maker, especially if you have a trained Sales Ninja doing the phone work for you. You should also Text message the seller or possibly email them if you have their email address (not likely). Personally, some of our best and biggest deals have come from calling back Hangups. It's best if you can call them back within 15 minutes, however these leads can still be good 12+ months later!
If you need assistance calling your hangups or working your leads, you may want to consider the REIvault Sales Ninja Phone Team. Here's a link to learn more: www.REIvault.com/SalesNinjaTeam