After I run a testnet node and synchronize it, I start mining.After I get some cheatcoin, stick to mining. After a while, when I check again, the balance is missing. Please explain what happened 
Code:
Statistics for ours and maximum known parameters:
hosts: 176 of 176
blocks: 9570 of 9570
main blocks: 2517 of 2517
orphan blocks: 2
wait sync blocks: 0
chain difficulty: ef236c7cb4dacc3dfc of ef236c7cb4dacc3dfc
cheatcoins supply: 2577408.000000000 of 2577408.000000000
cheatcoin> balance
Balance: 4096.000000000 cheatcoins
cheatcoin> balance
Balance: 5120.000000000 cheatcoins
cheatcoin> balance
Balance: 0.000000000 cheatcoins
cheatcoin> balance
Balance: 0.000000000 cheatcoins
cheatcoin> stats
Statistics for ours and maximum known parameters:
hosts: 176 of 176
blocks: 10255 of 177032
main blocks: 2620 of 18051
orphan blocks: 8
wait sync blocks: 692
chain difficulty: f3dedeedb1130a3477 of 12e4f98379d7f4cc0ccb
cheatcoins supply: 2682880.000000000 of 18484224.000000000
hosts: 176 of 176
blocks: 9570 of 9570
main blocks: 2517 of 2517
orphan blocks: 2
wait sync blocks: 0
chain difficulty: ef236c7cb4dacc3dfc of ef236c7cb4dacc3dfc
cheatcoins supply: 2577408.000000000 of 2577408.000000000
cheatcoin> balance
Balance: 4096.000000000 cheatcoins
cheatcoin> balance
Balance: 5120.000000000 cheatcoins
cheatcoin> balance
Balance: 0.000000000 cheatcoins
cheatcoin> balance
Balance: 0.000000000 cheatcoins
cheatcoin> stats
Statistics for ours and maximum known parameters:
hosts: 176 of 176
blocks: 10255 of 177032
main blocks: 2620 of 18051
orphan blocks: 8
wait sync blocks: 692
chain difficulty: f3dedeedb1130a3477 of 12e4f98379d7f4cc0ccb
cheatcoins supply: 2682880.000000000 of 18484224.000000000