Definitely highly probable. Which client are you using as a wallet? If you are using a desktop wallet, you would most likely be able to get the raw transaction and broadcast it yourself.
Those transactions are payouts I got from a cloud mining service. Maybe they create transactions using Chain.so and pay low fees, the transactions were in Chain.so'queue and not even in the mempool(and maybe Chain.so's explorer shows transactions in the queue as well). And after days it finally got broadcasted into the network.